How can I repair couple of loose pasta floor tile in my old house? The tiles are loose causing the grout to crack. I do not want to remove it, re-glue, re-grout if possible. Thanks

It may not be "professional" but I have done something like this before and it works. Try to inject adhesive into joint with a syringe. Get a needle from the vet or a pharmacy and use super glue or a silicone. It may hold for another 50 years and if not, you haven’t lost much by trying.

This technique will work but if you can lift those tiles up with suction cup or any similar gizmo you will have a chance to fix it properly.