Our PC is a 2007 2350. We ordered it without a slide-out because of the potential for trouble with age, especially trouble with water. Now that PCs are aging, people are posting issues with their slide-outs which unfortunately is not surprising.
What troubles me more are the posts of water mysteriously leaking in the frontal transition area. That should be one of the more reliable connections. Motor homes in general take a beating when being driven, with so much vibration and jolting. Still a PC is supposed to hold up to that.
Finally getting to a project I planned a year ago, last August I attempted to reduce that beating in the forward part of our rig by changing the front springs to softer ones that better match our actual load. CLICK HERE
to read about the project which includes many pictures. My confidence in doing this seeming radical modification was fueled when I learned our front coil springs were the exact same ones installed on an E450. I weighed our front axle twice, once with the rig empty, and a second time loaded up during a trip with us sitting in the front seats. I used those weights to determine how soft of a front spring our rig needs with some margin to spare. Since the change in front coil springs, our comfort up front is noticeably softer which our PC also appreciates.
To be clear, this modification does not apply to every PC model. But maybe some models with their front axle payloads should be evaluated. One easy thing everyone can do is to weigh your rig during a trip with you inside it, then adjust your tire pressure based on that weight. More air than required translates to a harder ride than necessary.
Back to the subject, I hope you figure out soon, how water is getting inside. Every PC owner should monitor this thread.