Jimy, you can configure your mod_jk to log more and you will see what was happening with the request (the logging will be however too verbose so not a good fit for production for sure).
If there are chances you can reproduce than surely +1 for Byteman if you want to instrument a class/method to do additional logging.
BTW "But there is no hs_error" - did the JVM user have permission to write it there? Make sure you are not calling System.exit() ;-)