The sides appear to be bowing in unequally. I measured the depth and the variance between support locations and down the middle was no more than 3/4 inch. Mostly 1/4 inch to 3/8 inch.
The jack you are talking about is it a high lift jack? How much water did you drain off? Where and how did you position the jack so not to damage pool? Can you post any pictures. I have three broken pavers.