I took apart the pre-hung door unit (trim just tacked loosely in place) in my bathroom, lowered the door 1" (since the builder had raised it "for tile" but it was higher than linen closet door right next to it). We separated the trim from the jamb to make it easier to cut (floor already installed). The joints came apart, so I finished each piece separately. Got the jamb set, door hung, went to put up trim and top piece won't meet sides. Turns out the header was installed about 1/16" pushed into the room, never noticed the bow when patching/painting, or when the trim was loose, but now when side trim is flat to the wall, the top trim is pushed out and also gap at reveal since the header/sheetrock is sticking out farther into the room than the top part of the jamb is.

I'm not going to pull the jamb out again and tilt the door into the room. So should I plane the back of the top piece of trim, or should I do as my cousin suggests and biscuit join the trim together again, mark the top, and cut out the sheetrock so that the top piece of trim is actually recessed in (but meets in the front of the mitre joints)? Or just nail up the sides, do the same thing w/o joining first?

This isn't the first framing problem we've found in our modular home, just the latest.