feedback on these units is a simple 10kOhm pot and very easy to replace.
Remove the drive unit cover (carefully, there are connected wires) and replace the pot. Just get one with the same dimensions, pay attention to the 3 wires and where they go. The pot is "centered" when the ram is in it's mid-stroke position.
You can check the pot, At either end of the stroke, center to end terminals should read either 0 or 10K-ohms, and both read about 5k-ohms with the ram centered.
How old is the unit? Motor
on the older units (pre 2000-ish?) are no longer available but might be repairable by a good motor
repairman. Newer units might be found, but I have not looked for them.