It happens switching between any of l the platforms I use, PC/Mac, Android, and iOS. I get more or less errors depending on what is in the current scene in the editor. If I switch platforms with a blank scene open, I get no errors.
If I examine the Mesh Renderer component on any of my tk2dTextMeshes, I can see the the Material looks wrong. Instead of saying atlas0 material, I see something like tk2dInternal$.Material_Stones@1x_atlast0 material. The name of my sprite collection is 'Stones'. I guess that the file association has been broken in all my text prefabs? Rebuilding the sprite collection doesn't fix the issue. Any ideas? Thanks for your help.