I would start by looking up on the roof for any sign of bad caulking on that side of the roof. My guess is that your front AC unit is leaking where it is lag screwed to the roof. Lay down and see if you can see the two screws that hold your front ac unit down They are run through the frame of the AC unit, through a spacer and then into the roof. You don't need to open the AC unit as they are external. I caulked around mine with alpha systems self leveling caulking available from Amazon. The other possibility on your unit would be around the antenna which is also on that side of the roof. My rear AC unit leaked right from the factory and the water came out of the return air opening in the ceiling. The cause was not obvious but my dealer told me it was common for the AC fasteners to leak so I caulked them all and have not had another leak. Don't be afraid to use a lot of caulk and squirt it on top and under the bracket where the fastener goes through the roof.
2018 Redwood 3901WB pulled by 2016 Chev 3500 HD DRW. Goodyear G114 tires, Moryde I.S., Kodiak Disc Brakes, Splendide W/D, Tire Minder TPMS, Sleep # King.