We had the identical same situation you are describing in an ex-Monaco MH.
The dealer, Paul Evert's RV in Fresno, Ca. was directed by Monaco in Coburg, OR to cut short pieces of aluminum angle, insert in areas in the ceiling that was coming down, through light fixtures and vents. They would screw in the angled pieces from within and once fastened, they would screw up into the ceiling from below and into the aluminum angle. The screws were then covered with 1" wooden flat strips across the ceiling from one end to the other to match cabinet stain. Looked like a factory job and held up very well. If interested, you can call the dealer and I believe the technician that performed the work was Rod, Pat Clive (?) was the service writer.
Hope this helps, always something with RV's.
2008 Itasca Meridian
2010 Ford Sport Trac