Get your coffee and get comfortable, this is a long post!
I started at the front with the cover for the propane. First of all, the cover had big gaps at the seams and would not clear the chain hangers of my WD hitch. I had to loosen and slide the brackets forward just to open the cover. Second, I found the cover hard to open and even harder to close. Even the center latch was bent from the strain. To fix these problems I first removed the left gas strut and replaced it with a prop rod I made from 3/8 steel rod. I then removed the metal bracket nuts and raised the cover by 1/2 inch. I replaced both the nuts and incorrectly sized lock washers with locknuts. The cover is now aligned and opens and closes quite nicely.
If your trailer is like mine, if you look carefully underneath the body where the frame angles towards the tongue you will find two very large holes, one on either side, that lead into the trailer behind the dinette wall. I didn't want a family of raccoons moving in so I cut out the wall behind the cushions and filled the front area with spray foam. ( 7 cans!)
Most of the screws in the storage lids under the dinette cushions were loose, so I removed them all and dipped them in adhesive before putting them back in. I did this on all of the cabinets and drawer slide screws throughout the camper.
When the table was lowered to a bed, I noticed when my son sat on the edge, the table tipped to the point it looked like it was going break. I replaced the 2x2s under the table with 2x6s and added outriggers that fold down under the table when it is converted to a bed. It is much more stable now.
Most of the screws that hold the back of the kitchen cabinets to the wall were missing or had fallen out because they were screwed into the foam wall. I took a 4 foot piece of aluminum angle and screwed it horizontally to the wall studs. I then was able to attached the cabinets and gas line clamp to the aluminum.
The stove was just sitting loose on top of the counter so I siliconed it to the counter. I also cabled-tied messy wiring, re-aligned the cabinets doors, and fixed various other cosmetic issues.
I filled the plumbing chase in the water filter cabinet with spray foam. It looked like just the kind of place mice would love to get into.
I removed the grab handles outside the doors. They were pitting on the outside and full of water on the inside. I sanded and coated them to keep them looking nice. I drilled small drain holes on the bottom and siliconed around them after putting them back on. I also had to adjust the door latch as the dead bolt did not line up causing the keyless remote not to operate properly.
Like I posted earlier, I actually enjoyed doing the work and in spite of the terrible quality control, every time I step inside I still think what a cool trailer the Aviator is and don't regret buying it.
I hope this helps and other things you may come up with I would like to hear about.