I'm a fairly new owner (22D). I've been studying this coach and long term issues we may both encounter. This is one of them.
It is a known problem with material incompatibility in the hinges. A galvanic corrosion problem. There is only one solution. You have to service these hinges about every six months with anti-seize lubrication. One hinge at a time. I hope you can get them out.
Here is a pretty good description of the problem and a way to maintain the hinges:
https://www.bing.com/videos/search?q...tail&FORM=VIRE.
The part you want starts at 3:30.