Check the effectiveness your drip edge in the rear and if you see any rust along the bottom of your ramp door, make sure the drip edge along the top is doing its job and water is not getting inside the rear ramp. The weather seal should stop any water from getting in, but these doors are not perfectly flat and do not seal well. I suppose you could get a much thicker seal where it would compress more, but the seal is only a backup.. water should not be consistently getting to that top seal where water can just set there. The drip edge on this trailer did not stick out far enough in my opinion and it was also too high up. A good flow of water and winds flowing would push water up on the seal.
When I went camping in December I noticed that my flooring on the ramp door was coming loose right along the bottom 12 inches and I also noticed a little rusty water when I let down the ramp. I suspected I had a leak, but did not take time to look real close. I pulled the CTC in the driveway today to start getting ready to leave next Thursday AM and I removed the trim on the ramp and took a close look thinking I just needed to re-adhere the flooring. Nothing rotted yet thankfully, but if the flooring had not started to come loose I would not have noticed and damage would get worse. Basically, the drip edge is not big enough and water finds its way on the rear seal and then between the plywood and frame of the door.
I bought some 1.5 In Aluminum Angle stock today and built out the drip edge to cover the door seal and after some rust conversion chemical dries tonight, I will be taking Eternabond tape and sealing the edge where the plywood attaches to ramp door frame by taping across the aluminum trim I installed to the door frame itself.. That appears to be where it was leaking as water found its way there. I could see a slight gap there where the plywood was not flush to frame.
Tonight I have the flooring pulled back and held with the AC on in the camper and a fan blowing on the wood. Hopefully it will dry up and I can re-adhere the flooring before I leave. The issue was just along the bottom 12 inches or so where gravity took the water. Past where the flooring is pulled back, adhesion is tight and I really cannot pull it loose without stretching the flooring... so it is good there,
The damage: You can see where some water wicked along the trim on the bottom also. We had some torrential rains a few weeks back and I suspect that is when most the water got in.. but it has been leaking a bit for a while now , obviously. The trailer sits on the parking pad slightly tilted to the back so water runs off the back mostly.

Where the water was getting in

Drilled 1.5 Angle stock and screwed to existing drip edge and caulked.

That is a serious drip edge now!

Water coming off the roof will clear the door and nothing should get onto that seal. If it does however, I will also seal fron the aluminum trim strip to the frame with some eternabond tape. Nothing will get in.
