Lots of threads on it but it’s a design flaw not a sealant problem. The band is riveted to steel plates, over 50 of them. Over time the plates rust out, rivets pop and the
fiberglass bulges too. Prepare for a project. Anyone can do it, covered work space helps a lot.
Trilliums are great, I have one. But the vintage ones had known design flaws: belly band, frame, door hinges and body to frame bolts. Then you have age issues unrelated to brand like resealing
windows,
axle replacement and poor power control center.