I use single atlas per file with a few skeletons. As I have 2048 size as maximum, spine creates 2 atlases on export. Sprites belong to one of skeletons appears to be placed on both atlases: a part of them on the first, a part on the second. And then the problem appears. In Mesh Renderer I see 3 materils instead of 2, the third material duplicates 1st somehow. http://joxi.ru/nAyzzJ9ugPaVRr
And the problem appears in the game. A part of the first atlas renders in the first material and a part in its duplicate somehow. When I zoom in the game materials 1 and 3 switches for the moment and I see a blinking of a shadow sprite. You can see it on this video:
https://drive.google.com/file/d/1zTGsfqbtDRzdfqt_nIUtJSGG76sVYNoO/view?usp=sharing