In a 1993 Florida slab-built home, we have a custom tile standup shower. Just noticed the drain assembly has recessed about 3/8" below the tile and there is space above the grate that the water can run out of into the slab.

The whole drain assembly can be moved slightly up and down (1/4 " when stepped on) as if the PVC drain pipe is moving in the soil under the slab.

All that is visible from the shower is the hole in the grouted tile floor and the now recessed drain grate with white PVC showing below it. Didn't see the pan when built, so I don't know how drain was constructed or standard practices for them.

Any ideas on how to repair?