java.lang.IllegalStateException: Transaction not successfully started

One of our customers is experiencing an unusual error. Our app tries to copy a page tree using pageManager.deepCopyPage(). When it finishes, the completedSuccessfully property of the progress meter is false, but there are no error messages in the status.

In the log, I can see the following stack trace:

java.lang.IllegalStateException: Transaction not successfully started
	at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:63)
	at com.atlassian.hibernate.util.TransactionHelper$RestartOnCommitTransaction.commit(TransactionHelper.java:45)
	at com.atlassian.hibernate.adapter.adapters.TransactionV2Adapter.commit(TransactionV2Adapter.java:30)
	at com.atlassian.confluence.impl.hibernate.bulk.HibernateBulkTransaction.commitTransaciton(HibernateBulkTransaction.java:64)
	at com.atlassian.confluence.impl.hibernate.bulk.RecursiveHibernateBulkAction.commitAndUpdateProgress(RecursiveHibernateBulkAction.java:142)
	at com.atlassian.confluence.impl.hibernate.bulk.RecursiveHibernateBulkAction.executeInternal(RecursiveHibernateBulkAction.java:126)
	at com.atlassian.confluence.impl.hibernate.bulk.RecursiveHibernateBulkAction.execute(RecursiveHibernateBulkAction.java:55)
	at com.atlassian.confluence.pages.persistence.dao.bulk.copy.DefaultBulkPageCopy.deepCopyInternal(DefaultBulkPageCopy.java:195)
	at com.atlassian.confluence.pages.persistence.dao.bulk.copy.DefaultBulkPageCopy.deepCopy(DefaultBulkPageCopy.java:151)
	at com.atlassian.confluence.pages.DefaultPageManager.deepCopyPage(DefaultPageManager.java:666)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:295)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at com.atlassian.spring.interceptors.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:16)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at com.atlassian.confluence.util.profiling.ConfluenceMonitoringMethodInterceptor.invoke(ConfluenceMonitoringMethodInterceptor.java:36)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
	at com.sun.proxy.$Proxy150.deepCopyPage(Unknown Source)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at com.atlassian.plugin.util.ContextClassLoaderSettingInvocationHandler.invoke(ContextClassLoaderSettingInvocationHandler.java:26)
	at com.sun.proxy.$Proxy334.deepCopyPage(Unknown Source)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.doInvoke(ServiceInvoker.java:56)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.invoke(ServiceInvoker.java:60)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invokeUnprivileged(ServiceTCCLInterceptor.java:70)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invoke(ServiceTCCLInterceptor.java:53)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.eclipse.gemini.blueprint.service.importer.support.LocalBundleContextAdvice.invoke(LocalBundleContextAdvice.java:57)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
	at com.sun.proxy.$Proxy3022.deepCopyPage(Unknown Source)
	at com.k15t.scroll.documents.document.ServerCopyInstanceTask.doRunInTransaction(ServerCopyInstanceTask.java:282)
	at com.k15t.scroll.documents.infra.Transactor.lambda$transact$0(Transactor.java:20)
	at com.atlassian.sal.core.transaction.HostContextTransactionTemplate$1.doInTransaction(HostContextTransactionTemplate.java:21)
	at com.atlassian.sal.spring.component.SpringHostContextAccessor.lambda$doInTransaction$0(SpringHostContextAccessor.java:70)
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
	at com.atlassian.sal.spring.component.SpringHostContextAccessor.doInTransaction(SpringHostContextAccessor.java:68)
	at com.atlassian.confluence.spring.transaction.interceptor.ConfluenceSpringHostContextAccessor.access$001(ConfluenceSpringHostContextAccessor.java:21)
	at com.atlassian.confluence.spring.transaction.interceptor.ConfluenceSpringHostContextAccessor.lambda$doInTransaction$3(ConfluenceSpringHostContextAccessor.java:72)
	at com.atlassian.confluence.impl.vcache.VCacheRequestContextManager.doInRequestContextInternal(VCacheRequestContextManager.java:84)
	at com.atlassian.confluence.impl.vcache.VCacheRequestContextManager.doInRequestContext(VCacheRequestContextManager.java:68)
	at com.atlassian.confluence.spring.transaction.interceptor.ConfluenceSpringHostContextAccessor.doInTransaction(ConfluenceSpringHostContextAccessor.java:72)
	at com.atlassian.sal.core.transaction.HostContextTransactionTemplate.execute(HostContextTransactionTemplate.java:18)
	at jdk.internal.reflect.GeneratedMethodAccessor276.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at com.atlassian.plugin.util.ContextClassLoaderSettingInvocationHandler.invoke(ContextClassLoaderSettingInvocationHandler.java:26)
	at com.sun.proxy.$Proxy205.execute(Unknown Source)
	at jdk.internal.reflect.GeneratedMethodAccessor276.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.doInvoke(ServiceInvoker.java:56)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.invoke(ServiceInvoker.java:60)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invokeUnprivileged(ServiceTCCLInterceptor.java:70)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invoke(ServiceTCCLInterceptor.java:53)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.eclipse.gemini.blueprint.service.importer.support.LocalBundleContextAdvice.invoke(LocalBundleContextAdvice.java:57)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
	at com.sun.proxy.$Proxy3036.execute(Unknown Source)
	at com.k15t.scroll.documents.infra.ServerTransactor.transact(ServerTransactor.java:18)
	at com.k15t.scroll.documents.infra.Transactor.transact(Transactor.java:19)
	at com.k15t.scroll.documents.document.ServerCopyInstanceTask.doRun(ServerCopyInstanceTask.java:92)
	at com.k15t.scroll.documents.task.AbstractTask.run(AbstractTask.java:59)
	at com.k15t.scroll.documents.util.UserContextAwareRunnable.run(UserContextAwareRunnable.java:27)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)

The system is running Confluence Server 7.4.6.

Has anyone experienced such an error before? What could be the reason?