While not exactly that problem I had a water line break inside the wall in water heater closet (exterior access mechanical closet / storage room) in the sticks and bricks house a couple of years ago, leading to all sorts of mold and mildew growth. I treated it using a commercial ozone generator, running it for 12 hours per day, 3 days in a row with a box fan running for air circulation (Ozone will tend to settle to the lowest point if not stirred up with a fan), which seems to have been effective at killing everything that was growing. The unit I have is an older commercial unit, which is rated at 2.65 grams per hour of ozone, commercial units built in the last few years can output much higher amounts. Note Ozone is an inhalation hazard, so should not be used in occupied spaces, it will also kill plants so don't leave anything you don't want dead around it, and ventilate the air for at least an hour, preferably two hours before entering confined spaces where an Ozone generator has been running. Also note Ozone will degrade rubber and plastic, and using at too high of concentration can cause Ozone odor to persist for several days, so bigger is not always better. For an RV size space you probably want between 2 - 4 grams per hours Ozone production rate, Ozone has a half life of about 20 minutes in air, so using too small of unit may result in never reaching kill level saturation in a larger space, even with extended run times.
p.s. this is the unit I have https://carwashworld.com/product/oasis-plus-ozone-generator-deodorizer/ though thankfully I did not pay anywhere near the new unit price, mine was an old stock product covered with dust at a substantial discount, mine is also blue not black.
