bathtub liner problem

In 2004 we had a liner installed over our bathtub. We have been totally satisfied with the liner and quality of the work until recently we noticed there is water between the liner and the tub. There is no evidence of any defect in the caulking and no other obvious indication of how water could have gotten in. Is there any "fix" for this problem?

The problem I hear about is always around the drain port.

IMO, lining a tub is like smoking cigars because they are better for you than cigarettes.

The water go in around the perimeter or the overflow opening. The drain is TIGHT, otherwise the water would have drained out. You have to remove the drain "strainer" so the water can drain, and then put it back in. That has been a problem with just about every tub liner I have ever seen.

Thanks for the advice, hj. I am not a plumber so please excuse dumb questions. The liner was installed with a drain "stopper" that is pulled up to open and pushed down to close the drain. It was no problem to remove that. It screws in to a cross piece lower down in the drain opening. I think what you are suggesting is to remove the flanged assembly into which the stopper mechanism fits. I don't know if that is somehow screwed into the original tub drain opening or more of a friction fit, possibly with an o-ring or similar seal. Or could the drain assembly have been attached to the liner with a large nut on the bottom of the liner before the liner was dropped into the tub? Bottom line, I don't know for sure what my next step should be and am not yet to the point where I don't care if I rip up the liner.