Leaks on corners of Comet hardside

[Altair]

Hello, I am presently looking to buy a Comet hardside. I visited two 2015s already, but one had the rear right corner floor saturated with water. I tested with a Moisture Meter. The second one had all the four corners saturated with water.
I did a search on the net for clues as to the source of this problem, but didn't find much.
Do any of you have info on a permanent solution to this problem, in the eventuality that I would buy & restore one of them?
Thanks!

Altair