When you drain a vinyl liner the liner no longer has the weight of the water holding it down and it will shrink. When you go to refill the pool it is nearly impossible to get the vinyl to stretch back out enough to go back into place. Most of the time the tension will tear the vinyl before you get very far in refilling the pool. Sometimes, when the liner is less than one year old and you have a very warm sunny day it can be gotten to stretch enough but even then it can rarely be gotten to stretch just right to go back into place at all evenly. If you have a high water table things can be even worse, shifting the ground under the liner enough to cause problems putting in a new liner.
Plaster pools are often alright, but if you have a high water table the pool can float right out of the ground. That will tear the plumbing out, damage the coping and often the deck as well, and cause the ground under the pool to shift. When the pool settles back down it will almost never go back to where it was and will often crack or even split in two.
