Hi Gilby,
This is an odd problem. Are you running into this issue after reloading a class with JRebel? Could you send a full jrebel.log file to support@zeroturnaround.com after recreating the issue? If it is recreated after reloading a file with JRebel can you also send the full absolute path to the Class that was reloaded as well. Here are steps on how to configure JRebel logging:
https://zeroturnaround.com/software/jrebel/learn/sending-log/
Additionally, I see that you recently posted another error to the forums, is that problem occurring with the same project? Do you think it would be best to investigate the two issues separately?