RV Roof top A/C Units drip condensate INSIDE when evap drip pan drain holes are clogged.
Not familiar with Phaeton set up....whether drip pan drains out onto roof and then runs off or down tubing thru coach to ground
But drip pan is overflowing......fan wheel pulling overflow into discharge plenum
Just remove air return filter and check drip pan level
Roof gasket may NOT have needed replacing.
4 hold down bolts are used to secure A/C Unit to roof.
Gasket is 1" thick and should be compressed to about 1/2".....hold down bolts are just 'SNUG' to do so.
They can vibrate loose.....SNUG is a technical term (40 INCH pounds----INCH not Foot) that is hand tight and then just a snug up with wrench
TOO tight.....gasket can get squished and block drain holes in evap drip pan