Plugin container accessor is null

bamboo
exception

#1

One client came to me with the following exception:

java.lang.NullPointerException: Plugin container accessor is null. Plugin: com.stellarity.bamboo.tfs-repository-plugin. Module name: com.stellarity.bamboo.repository.TfsRepository.
    at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:250)
    at com.atlassian.plugin.module.ClassPrefixModuleFactory.createModule(ClassPrefixModuleFactory.java:32)
    at com.atlassian.plugin.module.PrefixDelegatingModuleFactory.createModule(PrefixDelegatingModuleFactory.java:88)
    at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor.createModule(AbstractBambooModuleDescriptor.java:26)
    at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor.access$000(AbstractBambooModuleDescriptor.java:17)
    at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor$2.call(AbstractBambooModuleDescriptor.java:91)
    at com.atlassian.bamboo.plugin.BambooPluginUtils.callUnsafeCode(BambooPluginUtils.java:53)
    at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor.getModule(AbstractBambooModuleDescriptor.java:99)
    at com.atlassian.bamboo.plugin.descriptor.RepositoryModuleDescriptorImpl.getModule(RepositoryModuleDescriptorImpl.java:61)
    at com.atlassian.bamboo.plugin.descriptor.RepositoryModuleDescriptorImpl.getModule(RepositoryModuleDescriptorImpl.java:26)
    at com.atlassian.bamboo.vcs.configuration.legacy.LegacyRepositoryModuleDescriptor.getLegacyModule(LegacyRepositoryModuleDescriptor.java:270)
    at com.atlassian.bamboo.vcs.configuration.legacy.LegacyRepositoryModuleDescriptor.getName(LegacyRepositoryModuleDescriptor.java:128)
    at java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469)
    at java.util.Comparator.lambda$thenComparing$36697e65$1(Comparator.java:217)

He upgraded Bamboo from 5.12 to 6.5.0. The exception happens on cloning a plan. Are there any clues how to troubleshoot the issue?