ConfigurationCacheHackList cannot be serialized

[mpkorstanje]

In our builds, we intermittently see:

https://github.com/junit-team/junit-framework/actions/runs/30542951097/job/90871874631?pr=5931

    FAILURE: Build failed with an exception.
    
    * What went wrong:
    Execution failed for task ':junit-jupiter-api:spotlessJava' (registered by plugin 'junitbuild.spotless-conventions').
    > Cannot fingerprint input property 'stepsInternalEquality': value 'com.diffplug.spotless.ConfigurationCacheHackList@5093751f' cannot be serialized.

And in the Develocity build scan this includes:

Cannot fingerprint input property 'stepsInternalEquality': value 'com.diffplug.spotless.ConfigurationCacheHackList@5093751f' cannot be serialized.
> java.io.IOException: Failed to provision P2 dependencies

Versions:

• Gradle 9.7.0-rc-1
• Spotless 8.9.0