In every Katalon Project you can find a folder named .cache where KS/KRE caches the compiled classes of Keywords.
The .cache folder is automatically created by KS/KRE so it is safe to delete.
Please try deleting the .cache folder.
I guess in the KRE project you have a corrupted binary of your keyword so that you should clean the cache. I believe KS/KRE has a subtle bug about the .cache; but it is easy to fix. Just remove it.