Concrete tile roof - 15 years old - see the sag over the center of the garage? Header over the door drops about 1 1/2" at middle - thinking this is the cause …from inside, trusses are intact.
Tiles are laid on battens only. There is no decking or underlayment. Not sure if this is correct.
See photo of the “coated cardboard” panels underneath the tiles. Many of these are cupping at the the seam overlap. Heat maybe? Or possibly moisture/humidity or leakage?