I don't have that RV but it does sound like time to look at better tools for working with the various types of sealers on RV.
When you mention damage to the fiberglass, it tells me you are using the wrong tools!
Try one of the various oscillating tools with a flat blade for working on the getting the old caulk or sealer off.
I first had a "brand name but it did not last long, once I found how well it worked on so many projects, both on the RV and on the house!
So I now use this "cheap" one and find it works the same and is lasting longer!
https://www.walmart.com/ip/Hyper-Tou...0&from=/search
Using a flat scraper blade that is thin enough to bend easily to fit flat on the fiberglass, it both does the work much quicker but since it is not forced hard into the work, it also has little chance of damage. It takes a thousand small bites instead of that one big one we use when doing it by hand!
With an RV on hand, redoing the seals is a constant!