musty

The musty smell is probably in your carpet or soft upholstery now. You can rent a small ozone generator to remove most odors from your coach. They use them to remove smoke odors after a fire.

Very likely that our roof A/C EVAPORATOR needs to be cleaned. It is done from the roof, after removing the shroud and then the cover for the evaporator.

A "wet dog" smell when you first turn on the unit is a sure symptom of this issue.

Any box store will have evaporator cleaner (NOT condenser cleaner which is for outdoor use).

Suspect you will be shocked at what you find!

Lots of threads on how to clean evaporator - most RVers tend to overlook the evaporator as it's tough to get too. I have never used any special cleaner to clean mine - just have to climb up on the roof and remove the AC shroud and then remove a 15+ screws which hold down a metal cover on the front of the AC system. Make sure you put some towels in the hole between the roof/outside and turn off the AC/DC.