It was broken, sort of. The middle hallway doors just sort of hung there.
I took off the old one (photo 1), replaced it with a new one (photo 2). But the 2 doors didn't meet correctly, which was part of the original problem. Getting them to fit would require lowering the strike plate. Photo 4 shows where I started. Movie clip 1 shows me drilling out the new mortise an inch lower than the old one.
Photo 5 shows chiseling I needed to do to recess the strike plate. The old one was simply screwed onto the door frame (with round head screws no less), and looked bad. Photo 6 is a demo of chiseling, but not an action photo (use 2 hands for sharp blades). The next to last photo shows the plate target while the last photo shows the screw being started. The old screws were probably 1/2 inches long and the new ones over an inch.
The final video is the door closing with a satisfying clunk.