i'm about to move into a rental house where one of the bathrooms has all original (and slightly beat up) tile & fixtures. the tile floor is the old white hexagon tiles, laid in sheets. in the center of the room, there is an area 2' by 2' where it feels like the tile has become separated from the subfloor, and it slides ever so slightly under foot.

the owner is not in a financial position to renovate (and we don't want to deal with the dust). is there a sealer that can be poured over top to 'harden' the surface and reduce the movement?