Hi again NF:
At this point I would crack those tiles outta there and replace with closest matching tile possible.
The tiles will probably pop up pretty good, but if meet with resistance just give them a good few cracks in the middle of the tile to break into smaller pieces.
Most important here will be to not damage any tiles next to damaged tiles....so when removing the tiles and the
OLD THINSET MORTAR under tile
work toward damaged tile and away from good tiles, and remove the grout that surrounds each tile carefully so don't chip the good tiles.
Then want to use a
thinset mortar to set the tiles in. To be sure correct installation I add thinset to floor and then "butter" the backs of each tile so no voids under any tiles ever (buttering back just means to float a thin layer over the entire back of tile so entire tile covered). Just be sure not to go too thick...don't want new tiles higher than older tiles
Let tiles set overnight, then grout with matching grout color. Hopefully that will be the end of that...
Let us know what you think...Have good day ALL...Mark
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