Here is the link to my game, and I hope someone will solve this mystery that has been troubling my mind for a very long time…
https://scratch.mit.edu/projects/1255285711

I see a lot of instances of the “when I start as a clone create clone of myself”, and clones doing this through broadcasts as well.

Can't guarantee this is the only cause, but during my tests the final thread running before the crash always seems to be a bunch of clones from the same sprite.

Edit: I deleted these clone creating loops in the “hitbox2” and “snow” sprites. The game doesn't seem to crash anymore. But occasionally the framerate drops really low for some reason. Probably a different bug

Edit: the framerate also seems to drop when a ton of “particle” clones appear - I have deleted the “repeat 10” in this sprite

Edit: the framerate also drops when the reindeer sprite appears. Further inspection caused me to realise the code was stuck on “tree check2”. I have deleted this.

Edit: I played it for a while and no crashing or lagging happened! Wait the background sprite suddenly froze the game. Removed the graphic effect loops from both of the background sprites.
Ran the game for a while and no crashing or lagging seemed to happen.

do what you wish with the info I gained