Hi Ken,
Sorry to hear that you've been having keel-winch problems.
It does seem that your fault is likely to be in the control-electrics.
I'm not familiar with the Parker control system as Indianna has a bespoke system fitted by a previous owner. However, assuming that the Parker system consists basically of two relays, one for each direction of travel, maybe the down relay is working intermittently, or there is a high resistance connection in the wiring from cockpit-mounted switch to relay coil.
If the system does have two discrete relays, and they are of the plug-in variety, a simple first check might be to temporarily swap the relays.
Otherwise, you could try shorting the output of the down relay to bypass the control side of the relay circuit.
Regards,
Paul