We have a similar problem on our trailer. Although we caught it before the floor rotted, you can still see water stains on the slide floor. We have recaulked it regularly since new. But it would flex and break loose the caulking almost immediately. We had a tech work on it while at FROG. He said that type of trim is notorious for leaking and the screws holding it on from the bottom are not catching like they should. He took out the old screws and put in 3" screws to get back into the framing. Time will tell if that takes care of the problem. But we just got home from a 5,000 mile trip and the caulking is intact. So the longer screws might be something to consider when you replace the floor.