We had an overlapping liner put in this summer . Everything seemed fine . The pool was filled all summer then I noticed the overlap getting less on one side . The entire pool might avg 4” overlap ( not a lot but it was the only overlapping pool liner pool supplies sold for a 27’ 54” wall) when I seen it in July it might have had 2” over hang ( under the top rail ) and now in novemeber its probably down to 1” what could be causing my liner to slip when it was full of water for months . It’s brand new liner