That would be a real bad condition as you would be short cycling air, instead of the cold air from the coach interior you are running the supply air that has already been heated back through the furnace. Likely no damage was done as the unit has high limit thermostat that will open to prevent damage.
I would check to see if the furnace had moved in relationship to the duct work. If not and the ductwork cannot be moved then the aluminum SMACNA tape might be helpful. It is for sealing fiberglass foil wrapped duct work and is very durable and permanent. Home centers sell aluminum tape but it might not be the same quality.
Our coach has its water pump in the same compartment so I am in there annually and its pretty clean. One thing that did not jive was the furnace manufacturers free air spec and the square inches of hole in our wood grill were a little low but it is a non standard size so I elect to live with it. I save all the screws that were dropped and cast off
feeling that they might be useful somewhere else
lucky so far I am running a surplus