Class C overhead movement causing seal failure

If you are getting that much "flex" I would be looking
for water damage that has caused the front frame to rot.

Removing the interior paneling will expose the framework
and still allow the outside to stay together while you
inspect. Of course you would have to replace the paneling
and repaper or paint it. If it is in good condition or after
repairs it would also allow you to add insulation before
re paneling.