The only times my roof unit has leaked on me is when I let those four gasket adjustments described above get too loose.
You can gain access by dropping the ceiling unit cover where your Air Conditioner filter is located
google image
Google Image
Another time was during the night when the humidity was real bad and things started freezing up inside the air conditioner.
After everything thawed out the dripping stopped...
Since my unit is a POPUP and not all that air tight I think freezing up over nite with the air conditoner on all the time is somewhat common...
I have also heard one should have a fan blowing around in the trailer on those high humid nites...
I also always adjust the stablizer jacks to give me just a small amount of drop off on the back of the trailer roof for the normal air conditioner run-off... Better for us to keep the run-off going to the back side of the trailer verses the patio side...