Polyobjects have come a long way since Hexen but still have some... issues. They can be mitigated with careful level design, but as you could probably tell, I never actually finished that level.
Was it in the large room with the silver platform? That is the final boss and is meant to be challenging. The game is supposed to autosave at the beginning of every level, but it could be bugged. I could and should have set it up to autosave just before the boss fight but it just hadn't occurred to me.
But I mean, it's SBIG Jam, so these kinds of issues are to be expected. Glad you enjoyed it despite (or because of?) the issues.