Ben,

Thanks for the detailed explanation and description.

2 questions then:

1] After removing the coping and in the process of resetting it in place, would it be feasible to artificially widen the expansion joint by not quite placing the coping back in the original position but rather say 1/4- 3/8" more so in toward the pool and away from the deck? [yes it make appear a bit off overhanging the tile but if it can help eliminate the problem from reoccurring..]

2] Would you know if there is a specific type of mortar used for resetting the coping?

Thanks again for all your help

Rob