UV coordinates seemingly aren't applied correctly (?), causing visible seams between the mesh's faces

[Dshah_H]

hey, I think you need to offset your texture when you apply otherwise it leaves those artifacts, for example if atlas is 256X256, try to use only like 62X62 tile in your code , see more information from @PatrickRyan and @Evgeni_Popov here thinInstance multiple materials - #42 by PatrickRyan