OnMouseDown(), OnMouseOver(), and OnMouseExit() not working in build when certain skybox materials are used

(ORIGINAL POST) I recently made a build of a game where multiple tiles are highlighted and can be interacted with. It works without any issue in the editor, but when the game is built, this stops working in most of the levels. The methods are never called. However, in 3 out of the 22 levels in the game, it works without issue. I can't see any major differences between these levels. (UPDATE: The difference between them was the skybox material). Not even a Debug.Log command in OnMouseOver() triggers.

(UPDATE) I still haven't solved this, but I found the issue. It seems to be the skybox material causing the problem. When changed to the skyboxes used in the working levels, the issue goes away. However, I can't figure out why this is, as the skyboxes seem identical other than the images they use. Copying a working skybox material creates one that doesn't work. The appearance of the skybox is important to the levels' design, so I can't just switch to one of the ones that work. I really can't wrap my head around what could be going wrong, since an identical material to one of the working skybox materials with the only difference I see being the name still doesn't work.