Question Any Idea what could be Making my Game so Laggy / Stuttery

OK. My game is fine at first, it usually goes wrong halfway through level nine or ten. These levels are procedurally generated and are the exact same scene reloaded with a short intermission screen / scene between them.

No fans come on, the CPU monitor barely show a blip for any core -- you would guess there is no game running for watching that. The number of enemies in the level is no more, sometimes less, than on earlier level, and since the stutter starts halfway through a level many are already inactive (scripts and physics being disable at death). I don't have a go way to monitor the GPU, the scene isn't more demanding than before and has much simpler geometry and far fewer item than typical AAA and professional games that don't have the problem. EDIT: The persists when moving to a new level, despite the scene being reloaded.

This never happened when I was using Unity 2020 (which had other problems instead), but with 2021.3.4f1 its a real issue. Any idea what could be causing this or where I could look for solutions? Anyone else ever experience something like this?

 

Use the profiler.

 

Well, it may have been a bug in the engine version. I updated to 2021.3.19f1 and it seems to have been fixed (further testing required).