I can not start manually triggered build jobs. The jobs remain in the build triggered stand and wait for a free Build processor, although pleased processors are present.
Your issue is because your "Project Build Default Authorization", Groovy post build step does not work with "Run as user who triggered the build" if you remove this parameter from security the Groovy post build step will work.
This parameter is from Authorize Project Plugin, it runs the build as the specified user rather than the SYSTEM "default", causing the permissions check to fail, and this was changed from earlier.
Non-admin users should be unable to save/modify non-sandboxed Groovy postbuild scripts since Groovy Postbuild 2.0.