Can it be fixed? Yes, but it may require resetting. Hope you don't have expensive decking around it.
Who's paying? Depends on the warranty terms.

Yes it can be fixed but I would tend to think that you may have some kind of plumbing leak that is causing the pool to "settle" on one end. are you losing any water out of the pool?

The only decking I have is the concrete slab which is also sinking. I would hope that they would pay for it, if not I guess I would have to bring them to court. The pool is not loosing water. I belive the reason the pool is sinking is because the ground sloped where the pool was built and a good amount of dirt was added around the pool. I think the dirt was not packed well and is settling which is causing the slab to sink and in turn is bringing the pool with it.

The chance that the weight of your concrete slab is bringing down your pool is pretty slim. The water in the pool weighs a whole lot more than the concrete on the edge of it. Was the tile put on the pool shell before or after the pool was installed?

The tile was put on after the pool was installed.

When the pool was "set", what material was used to back fill, sand or 1/8" gravel?

Can you post some pix? Past and present will help us to help you.

The pool was backfilled with sand.

Was a sump installed? Is there water in it? As DonaldV asked, are you loosing water?

No sump. Not loosing water.

The only water source would be a drain that runs under the concrete decking which is abount ten feet from the pool. It is just a four inch pipe that runs to drain rain water.

Do you have a wide angle viewed picture to show us? We might see something.

Can I assume correctly that the tiles were attached with the pool nearly full? All looked OK then and over time, the deep end settled with the concrete?

I will try to get a picture. The tiles were fine but started to come off about a year later but only in some places. It is the shallow side that is sinking.

my deep end is 4 inches lower then the low end of the pool is this dangerous. can we still allow the kids to swim in it. thank you

We are having the same problem. I would love to hear how others have handled it. we have one end about 1.25 inches lower than the rest. I suspect it is because of a lawn sprinkler (no evidence it is leaking but and it has great output on entire zone however it is directly near the issue. Anyway, how much to fix it?