Above ground Pool soft in middle after having it installed.

We had a pool damaged this past winter and after removing the old pool the hole remained open for several weeks and filled up with lots of rain water. We drained the pool a couple of days before the installation but had heavy rains and lots of ground Saturation. The installer was very hesitant to put it in but after using the bobcat to clean up the muck he said that it was fine to install. We waited the 4 days to backfill as suggested by them. Now 10 days later my daughters tell me that the outside of the pool is hard but the middle is sinking in when they step there. My question is did the installers jump the gun and put it in before waiting until the ground was dry or will the pool eventually become hard in the middle. I am also concerned about the main drain sinking down. I just don't remember the first pool being soft in the middle after installation. Thanks for your help.