Error building for Confluence 9.5.2 - com.atlassian.pom:closedsource-private-pom:pom:7.0.15

When confluence.version is set to 9.5.1, my project builds & runs successfully.
When set to 9.5.2, atlas-clean && atlas-run yields the following build error (formatted slightly for readability):

[ERROR] Failed to execute goal com.atlassian.maven.plugins:confluence-maven-plugin:9.4.1:run (default-cli) on project [REDACTED]:
Unable to find/resolve artifact.:
 Failed to read artifact descriptor for com.atlassian.synchrony:synchrony-proxy:war:4.0.9:
 The following artifacts could not be resolved:
 com.atlassian.pom:closedsource-private-pom:pom:7.0.15 (absent):
 com.atlassian.pom:closedsource-private-pom:pom:7.0.15 was not found in https://maven.atlassian.com/repository/public during a previous attempt.

At face value, it would seem that synchrony-proxy:war:4.0.9 has a dependency on a private, closed source package?

pom.xml (abbreviated)

  ...
    <dependencyManagement>
      <dependencies>
        <dependency>
          <groupId>com.atlassian.confluence</groupId>
          <artifactId>confluence-plugins-platform-pom</artifactId>
          <version>${confluence.version}</version>
          <type>pom</type>
          <scope>import</scope>
        </dependency>
      </dependencies>
    </dependencyManagement>
...
   <properties>
        <confluence.version>9.5.2</confluence.version>
        <confluence.data.version>9.5.2</confluence.data.version>
        <amps.version>9.4.1</amps.version>

Not sure if this is the correct place to look, but for what its worth, 4.0.9 is not listed at all here:

https://mvnrepository.com/artifact/com.atlassian.synchrony/synchrony-proxy

The missing synchrony-proxy 4.0.9 has now appeared in maven.