ok
for starters the beeping is the system seeing the handle out of neutral position. If the handle has alot of play in it this will occur and the detent springs need to be replaced. Also if it is having a tendency to move without moving the handle when you press the deadman pedal the potentiometer may have a bad spot in it near the neutral position causing the voltage to fluctuate.
The beeping is caused by the handle moving away from neutral though.

Now you can go into the micro command menu using the default access of cat2 and find the option to do a Learn on the controls. (If the password has been changed and cat2 does not work then you will not get into the system without going through alot of trouble using dcat and a laptop).

If you gain access though and Once you re-learn the controls that beeping should stop. If it does not then you may be looking at a reman handle. Rebuilding them is not cost effective compared to just replacing it. Now this is important, do not change any other settings, just find the learn procedure and do that ONLY.