A trailer of that age the first thing I would look at are the axles.
Looking across to the other side of the trailer look at the trailing arm from the axles to the spindle. That are should have a slight downward angle towards the rear of the trailer. If the arm is level or a slight upward angle the axles are looking to be replaced.
While there are no definitive problems with that year that I know of I would take an ice pick along and poke through the rug just inside the door. If there is floor damage that is one of the first spots to look. Might poke around the toilet also.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles