What can be critical friezes?

Question

Unity

I have now made the main core of the game and just stamp the rooms, after a certain pack I check them first in the editor, then just on a PC and then on two smartphones, for two weeks on one phone a critical FPS slowdown was noticed with a complete freeze, and once during games and another time during the scene change, that is, the room ended and the scene began switching to level selection, there was no more on the same places, but on another phone (and it is much weaker) and the PC was not like that at all ...
Where I don’t know how to look, according to the code this should not be, and the fact that only on one smartphone this happened a couple of times in different places, and even when changing the scene, in general I don’t even know how to calculate what this could be from, I’ll note that on on the same smartphone in other games applications this was not noticed ...
What to do in such a case?

Answer 1

Profile and debug in this case.
And by the way, a complete freeze - it can be banal due to an error in logic - somewhere an endless loop or recursion without exit