Hello
The unit we are working on was installed in 1972 and had the exact issue of running correctly on inspection and in the up direction on auto.
However, on auto in the down direction as soon as it came off of the position switch it would stop and run back up to the floor.
The fix was adding a 250 Mfd cap between 24D and PC. This is mentioned in one of the manuals, Never needed it the first 54 years but does today.
