Given that it happens for me not just sometimes, but always, i think the problem has to lie with a difference between our computers/setups.
The possibilities i see are :
-The bug only happens on Linux, which would mean everyone who has experienced the bug played on Linux. That might easy to verify?
-The bug is due to something less specific than just playing on Linux, which would make it somewhat difficult to identify without asking a bunch of people to try to reproduce the bug.
-The bug is due to something that for some reason doesn't happen in a debug environment. If your tests included using a non-debug version of Cogmind (unlike in the GIF), then you already know the answer to that one.
-The bug is due to something that for some reason doesn't affect specifically your computer. For instance, maybe in the specific scenario of this bug, the game would try to get the stairs sprite from outside the game folder instead of the one already in the game folder¹. Then, upon failure, the game would default to using the stairs sprite instead.
In this scenario, the bug would not occur on your computer because the sprite the game tries to get does exist on your computer, but not on anyone else's.
¹Because of some error like using an absolute path instead of a relative one, for instance. Actually, i could try to verify that specific possibility myself... (even if this specific possibility makes a lot of assumptions about how the game works.)