Are you 100% sure that they are mortared down?
Did you see them being mortared down?
I think that you need an expansion joint, which means cutting with a concrete saw and then adding sealant.
As you can see below, there is zero room for the coping to sink without the pool sinking.
In my opinion, the stones need to be pulled up to investigate why they are high.
View attachment 625929

Coping being laid
