I noticed damp floor wood at one end of the slide and some rot starting. Turned out to be from a tear in the slide roof at the edge, so water was coming down the inside of that end wall and rotting the floor. I am pretending nothing is wrong with the inside of the wall once it dries out. (I don't know how to remove the end window and put it back, which I would have to do to look behind the inside wall.) :( I fixed the roof edge leak. The floor isn't that far gone I have to do anything if it stays dry now.
Total PITA, but as stated first fix the leak. Yes, cut away that soft rotten wood and put a good piece in to hold the bottom of the wall on (if the wall isn't also wet--water "wicks" up too) Just how to hold the new piece on the end of the floor so it still goes in and out is up to you! :) Maybe use thin steel plates above and below the joint?
