I had ceramic floor tiles installed in my home. Recently about a dozen tiles popped up, with the mortar still stuck to the back of the tile. Prior to installing these tiles I had removed old vinyl/asbestos floor tiles by scraping them up. A black film (the old mastic used to install the original tiles) remains on the concrete slab and I suspect that this film combined with seasonal temperature changes has caused the mortar holding the new ceramic tiles to loosen. What can I do to prevent this from happening in the future?