SBdad, I think what I see is the shower surround pulling away from the fiberglass shower. Is this correct? While I can't explain what happened to cause that, it should be an easy fix. At the same time you should be able to repair any leaks you may have had.
The enclosure is 3 panels plus the top rail and the 2 channels that attach to the shower stall. Begin by removing every screw you can find. 2 or 4 hold the side panels to the floor and there area several holding each panel to the wall channel and the door panel. Once all the pieces are removed, clean/remove all the caulk from everything.
Same goes with the shower stall where the panels attach to the bottom. On the wall channels, the bottom corners are square but the shower stall is radiused. Cut away the bottom corner of each channel so it fits the radiused corner better. It's then easier to get a good seal when you caulk. You will need to drill new holes to attach the side channels because the old ones must have stripped out somehow. I would use all new stainless steel sheet metal screws.
Once you re-attach the side channels, put a bead of silicone on the shower floor area where the walls will sit. The two side panels and door frame can go back in place at the same time. You will need some help with this. It's a bit heavy and awkward. Basically what your doing is removing, cleaning and re-assembling the whole unit with new screws in different locations. Pre-drill the fiberglass or it will crack & split.
I'll attach a few picture of when I did mine. Mine didn't pull away though. I did this to stop the leakage.