Sounds like a logic problem. There is a card for this in the A80. I worked on these back in the 70's. Cant remember but the edit mode is a logic mode to stop the takeup reel motor but engage the pinch roller.
Does the Take up motor run in fast forward and rewind? If it does not then there is a reel motor card and also pass transistors to drive the motor that could have problems. If the reel motor does work in fast forward and rewind than it is a logic problem. The Cards are under the transport and access is with a panel folded down.
These are great machines to work on and the Swiss made quality is superb but like everything else they break.
Good luck