respectfully, it's settlement.
not plumbing or anything along those lines. I can assure you there are no plumbing lines in that corner, it would take 2 days to drill through the concrete in a corner.
That pool drain (the white drain at the edge of the concrete) is probably filled with settlement and not functioning. Everytime we do pool decks and we rip up those drains - they're packed full with sediment.
The reason some pavers are higher is because the poured wall is not of consistant texture. I'll use the word "barb". The pavers are clinging to "barbs".
The patio needs to be re-done by a competent, EXPERIENCED contractor.
I can NOT stress the importance of prospective clients being well educated on paver installation, settlement, and so on, and the archives of this forum contain many posts from me stressing this.
All our prospective clients are provided with the following link. If your price providers are not locatable via this link - THEN DO NOT USE THEM: