Never had this happen before. Customer ordered mosaic tile. Traditional black and white checkerboard with 1" tiles. They are very thin, but packing says "for floors and walls". Mesh on back is quite dense. The mesh is bonding with the Mapei adhesive, but once dry, the tiles pop off! We have 3 more bathrooms to do after this one with the same tile. I think the backing and it's glue are the issues, but what can I do about it?