How to repair loose ceramic tiles without removing them?

Trying to fix the problem by injecting epoxy to fill voids in hollow sounding areas of the tile and to stabilize loose tiles is treating the symptom rather than fixing the problems. I have seen this attempted many times, and it never fills all of the voids and never fixes the problem. It normally buys more time hoping the problem goes away.

There is no way to know for sure the extent of the damage with an intrusive inspection, but if you have cracked grout that likely means that tiles are loose. It may or may not have anything to do with the tile bond to the substrate beneath it.It might be because the substrate under the tile is defective in some way. So injecting epoxy wouldn't help in that case.

There is a good chance that the tiles that are not hollow or loose now might become hollow and loose in the future because they might have the same underlying problem as the loose tiles.

The only way to know is to perform a forensic inspection by removing various tile under various conditions to see what the cause of the problem is, so the problem can be remediated rather than trying to remediate the symptom of the problem.

I would remove the wobbly ones and pull off the "hollow" ones if they come off easily. If you can get beside the "hollow" tiles you should be able to inject some base behind to solidify them. Then I would replace the loose tiles with new base and re-grout everything.

They do sell Glue in Syringes.,,,,,,,,,,,,,

Fix-A-Floor does work by re bonding the tiles to the subfloor and eliminating hollow tiles immediately by filling in the voids where the thinset has failed.