Hmm, you're right, the gameoverlayrenderer.dylib belongs to Steam.

Funny thing is, I've got Steam in-game overlay globally disabled... No idea what else I can do to prevent Steam from injecting its overlay lib into the game.

Factorio froze for no apparent reason, game log does not seem to contain anything to go by.

I've captured process perf sample using the OS's Activity Monitor app which shows most game threads stuck waiting on a mutex lock and others inside SDL library calls.