Water intrusion is the most common problem with any RV, as you are experiencing. Locating the leak source is very difficult. I recommend locating an RV service center that uses a SealTech Leak Detection System
. Once the source is eliminated, you may then successfully repair the damaged areas.
If you suspect water is running down the side of the slideout and wicking into a seam, you might try placing a length of waterproof tape diagonally along the sides of the outside wall of the slideout, and hopefully re-direct the water away from the floor area some.
Sorry I can't be more help.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"