Hi, Welcome to the site. Here you have access to the best resource possible for a vintage fibreglass trailer owner, other owners.
You have a problem that most of us experience. I have it four time over. The door hinge installation on these trailers is prone to failure after 30 years or so. One member described his door literally falling off at his feet. Filling the holes and re-drilling is not a bad idea. Others have gone so far as to add steel plates on the inside, by cutting holes in the pillar at the hinge side of the door frame.
Don't get me wrong, I really think fibreglass trailers rock, and you have one of the best, but there are some standard jobs that will need to be done. The wood around all the windows
rots and needs to be replaced. Just give your curtain rod holders a wiggle. If they feel like they are not screwed into anything, that is because the wood has rotted out from under them. Also, just search this site with the google custom search for the term "belly band". Each model of trailer has it's weak spot, in my opinion, the belly band on Trilliums is the week spot.
Re-install the wood around the windows
Close up the belly band
Deal with any frame/axle wear and tear
I believe that once those four major jobs are addressed, your trailer should be very low maintenance for the next thirty years. You may not need to do all of them now, but they will need to be done.