It sounds like your drain pipe has come apart under the shower or the drain is not tight.. try removing the decorative pc of metal which is inserted into drain, then try to tighten the drain in shower floor..if this appears tight then check plastic pipe under shower to see if it has come apart or is loose. The weak spot is due to not enough support under shower stall floor. Depending on access ,you should be able to secure floor with strips of wood.
If your unit is still under warranty talk to your dealer about fixing..