Al,
Welcome!!!
I can't recall the exact model year, but somewhere around the '06-'08ish Jayco had an issue with the roof they were using at the time. It is a felt backed rubber roof that would "wick" water from along the sides as I understand. Maybe some others will give the year(s) of the issue.
That is a good size rig so make sure you have the right tv. Also look into a good wdh with integrated sway control. The Reese Dual Cam, Reese SC, and the Equal-I-Zer 4 way system are all very good. The Reese hitch head (same for both models) does offer a little more fine tuning adjustment vs the Equal-I-Zer hitch head. The Dual Cam is a little more finicky in setting up. And may need minor tweaks if the tw (tongue weight) changes a lot: if the fresh water tank is in front of the axles- full vs empty.
As mentioned, check the tires. Most trailer tires have a lifespan of about 3-5yrs. There is a date code on the tires, possibly on the inside of the tire. Do not go by how the tread looks only, unless it has cracks (need replacement), but also the age of the tires. Always inflate to max sidewall pressure. IF you need to replace the tires, check to see the weight rating of the current vs the tt GVWR. If possible (and to close to each other) try to go up a LR rating if the wheel rating allows.
Look everywhere for water damage, the whole ceiling, along where the walls meet, any openings in the roof (vents, skylights, a/c, act), under all the windows, on the outside along the base of the floor/ outside wall area. Check all the appliances for proper operation.
The wheel bearings probably need to be repacked, and brakes checked.
Good luck!!!
