Hello!
Could you please send your trace and performance level jrebel.log file after reproducing the issue to support@zeroturnaround.com with the link to this forum topic? To generate it just add -Drebel.log=trace -Drebel.log.dump_stack_traces=10 -Drebel.log.perf=true to your VM arguments, restart your server and wait for it to become that dramatically slow.
Just to clarify – how long does it usually take for you to step over a code line while debugging?
Kind regards,
Valerie