727 stuck in third

It happens but not too often from what I've seen.

Unfortunately a lot of people neglect their trans.

It does sound like welded together direct clutchpack unless I'm just gettin old and wish I knew what I used to.
Bet that second gear band is burn't to hell and they changed the fluid so it looked clean.
The torque converter can dampen what you percieve as hanging up
Wish we could drive it and see.