On my 2017, it appears that the window seals are shot on the windows over the tv, the galley and the Murphy bed. It is an expensive fix. Is this common on Wonders? I live in the soggy northwest and need it fixed soon.
Sadly its pretty common for those to fail over time, as well as the gaskets around the bay door openings.
One maintenance item you can do (in the future) to help is wipe on 303 protectant every so often. That has UV blockers in it to help reduce aging. A small bottle like this Amazon.com: 303 Rubber Seal Protectant - Protects And Conditions Rubber... (https://amzn.to/407ETP4) can last a year or more and has the convince of an applicator. Personally I just use a larger spray bottle and a paper towel, use it on my tires as well.
That can be an expensive fix but one way to combat it would be to add an aftermarket warranty plan to your RV that covers leaks and seals. Just don't tell them there's a pre-existing issue. This will most likely cost more than doing a window seal job but will provide you with added protection against any future issues as well. If you find a good aftermarket warranty company through a reputable dealership it will cover all none standard maintenance related items on your RV including the chassis and leaks!