shop vac to remove wrinkles

Can anyone tell me if this has happened when using a shop vac to remove wrinkles in above ground pool?
I needed to have a spot in the floor of our 18 x 38 doughboy (w/deep end) fixed. We drained the pool, including the deep end so he could inspect the floor. After fixing spot, the pool guy put a small shop vac behind the liner near the deep end and we started refilling the pool. (Started refilling about 5p.m. day before yesterday). When I came home I noticed that there was an area near the shallow end where the rock had been dug out. (We backfilled around the pool with pea gravel (should we have?) Anyway it's about two feet deep outside of the shallow end. The next morning when I went to check on the pool, the liner in the shallow end of the pool had come loose and the pressure from the gravel had caused the walls to bow in. I called the pool guy, he came back, dug out the gravel, rehung the liner, but a bigger vac (bigger tube size) behind the liner and we started again. All was going well until about 10 this morning when the vac came loose again and the liner slipped in the deep end. (Pool guy is currently at my house now).
I'm starting to worry that maybe he doesn't know what he's doing and that the job that started at 250.00 to fix the pool krete spot, may be turned in to more.
I can say that we had another crew do this same work last year without any problems with the rock and liner giving, but they didn't use any type of vaccum to get out the wrinkles. They did it manually.
Any advice ?
Thanks
Kerrie