Cosmetic repairs to tile OK?

I have a 21 year old in ground, concrete pool. I had the entire pool refinished about ten years ago after the tiles fell off. The pool has a flagstone coping with an automatic cover with a track attached to the underside of the coping. Now the same problem with the tiles has recurred. I have two rows of 4x4 tiles. The top row is completely gone and the bottom row has a few tiles missing. I talked to a pool contractor about replacing the tiles. He told me that the pool surface itself is fine but I need to replace the coping as well as the tile since water is getting in around the back of the coping and causing the tiles to come loose. If I go this route I would be facing a very expensive job which would be made worse since it would make sense to replace the cover at the same time. I am considering selling the house next year and would like an unbiased opinion about whether I need to do such an extensive repair. The coping is solidly attached. I would prefer to drain the pool, replace the tiles and re-grout the existing coping and call it a day. My question is whether such a cosmetic repair is a reasonable approach. It seems to me to make more sense to fix the tile and do a more extensive repair later when the whole pool needs to be done. On the other hand, if it is difficult or impossible to effectively re-grout the in place coping and the tiles will start falling off immediately then I wouldn't want to take the cheap route. Does anyone have any thoughts on this situation?

Is there a flexible expansion joint between the coping stones and the rest of the pool deck? A pool will expand and contract vertically with the seasons. A pool deck will move horizontally. If the coping is mechanically attached to the deck it will move horizontally and the tile line will experience the difference in the movement of the pool and deck.

There is what could be an expansion joint. The joint on the edge of the coping stones that parallels the pool is a continuous rubbery caulk like strip. The grout between the stones is standard hard grout. The guy who looked at this a year ago said the expansion joint needs to be re caulked periodically. Of course he was the first guy to point this out in twenty one years. If we redo the tile without pulling the coping stones it looks (to ignorant me) like it would be fairly easy to recaulk the expansion joint. The grout sections might present a bigger problem since that material is hard and has a fair amount of cracks where water could leak. The impression I got from the guy who looked at it was that water penetration at the expansion joint is of greater concern.

It makes sense to me that if the expansion joint works and the coping moves with the pool that water behind the coping and tile would be the next likely culprit for popping the tiles. Wheter it's a deteriorated expansion joint or failed grout in the coping is really up to you or someone who's seen it.