I think you are in unknown territory. Who determined that fill void around pool shell with crushed concrete and compact accordingly was the correct fix? Was it a certified engineer? Was the fill void all done from around the edges of the shell?
We saw a pool in Texas that was built on unstable ground and developed cracks. The thread documented their engineers fix which involved braking a few holes in the bottom of the shell and putting in support under the bottom of the pool.
If the fill was only done around the edges how did you know what supported the bottom?
I hope the gunite shell has stopped moving as any flex around that flexible polyurethane repair will crack the plaster again. If this happens, you will have to repair the shell with staples. Hopefully not, though.