Groovy plugin script issue after upgrade to 6.5.1 from 5.1

Hi, I'm trying the upgrade procedure from 5.1 to 6.5.1 and something is not working correctly with the Groovy plugin. I installed the version for TC 6.5 but some customizations to the GroovyPropertiesProvider.groovy script are no longer working. Some properties I am adding to the build are no longer being picked up and dependencies on the existence of those properties imply that the builds which depend upon them are no longer starting. Below the code:

  private void addProductVersionAndAssemblyVersionParameters(BuildParameters parameters, SBuild build) {
     /*if(!build.isFinished())
          return;*/
          
     String buildNumber = build.getBuildNumber();
     
     Pattern p = Pattern.compile([some regex here]);

     Matcher m = p.matcher(buildNumber);

     if(!m.matches())
          return;
          
     if(m.groupCount() != 2)
          return;

     parameters.addConfiguration("build.number.productVersion", m.group(1));
     parameters.addConfiguration("build.number.assemblyVersion", m.group(2));
     
     LOG.debug("Calculated productVersion and assemblyVersion configuration properties for build type " + build.getBuildTypeId());
  }

It used to be working fine in version 5.1 but now I can't see them anymore. Note that I have other properties which are being set in the same way and are populated correctly, so there seems to be something wrong with these two. It might have to do with the lifecycle of a build perhaps? Note the commented code at the beginning of the procedure, initially I thought the build would have to be completed for this to be working correctly, but it was working fine in 5.1 with that snippet commented out.

Also, I can't seem to find a way to enable logging for this plugin, any advice?