Yep, you're absolutely right, that's the debug room. The fight crashes because if the game doesn't start correctly, certain variables aren't initialized.
That's my fault for uploading the wrong version. I pulled a file from my archives without checking whether it was a correctly packaged release.
I have since replaced that file with a brand new installer for v3.35 of Everlong. I recommend yourself and any players that attempted to play the v3.50 download remove that installation, and then reinstall the new download from the main page.
Thank you for bringing this error to my attention! There hopefully should be no issue with this fresh version, but let me know if there's any more problems!