4 speed A-833

Working on a 1971 Duster 340. On occassion the trans will get stuck in 2nd gear.
I can jack it up and move 3-4 a bit then it will come out of 2nd. I have the bayonet style shifter. All numbers matching car new to me. No history.
Have the shifter rebuilt? or rebuild trans? Or both?
Thanks in advance