Keystones says a drop of 1 1/2" is normal in ceiling.

Sounds similar to what a car dealer told me a few years ago, that a car using a quart of oil per 1000mi was normal :h I call that an oil burner. I would guess they would say that 1 1/2" drop is normal to avoid having to fix it. Where is the point that they would say there is a problem??

Is the roof sagging that much? The condensation won't drain, it will puddle.
I wouldn't accept that.

Sounds like there has been water damage to the roof from leak around A/C and it's now rotting and sinking.

Doesn't sound good at all. I know I'd be very concerned. Can you access the ceiling cavity from inside by removing the AC trim or nearby lights, speakers, etc? You might be able to see what's going on or feel by hand. Maybe you could take it to a reputable independent RV repair shop and get an inspection & report and submit it to Keystone and the dealer.

Met a Keystone TT owner in a CG once. His TT roof leaked like a seive from new. Dealer couldn't fix it so it got sent to the factory who only made it worse. He ended up fixing it himself. I think there is a difference tho. between east and west coast unit quality.

*Maybe* you can discover the cause and fix it yourself which you might be able to do better than anyone else anyway.

Agreed, not normal and definitely not OK.

Yeah, doesn't sound right. Third hand information is pretty suspect.

I don't think so..... Sounds like a problem.