I had the same problem with my Cayman windlass... severe corrosion in the base thanks to the very stupid idea of mounting it in a rubber footing that provides a perfect moat for seawater to attack the aluminium windlass. Also found base securing bolts ( stainless) corroded in the aluminium housing. An engineering firm sliced off the offending bottom and fashioned a new aluminium base plate, tapped to join to windlass and tapped for new mounting bolts. A similar size base plate of polypropylene was made out of a thick plastic cutting board to lift the aluminium out of the 'moat'.
I discovered the special hypoid gear oil had never been changed... a must do.
Connections for the electrics were found in the bulkhead behind the forward panel of the front V-berth. This looked very poorly done and the cabling in the chain locker under the windlass platform could be damaged by the anchor chain.
I made absolutely sure all wiring through this forward bulkhead was taken as high as possible, secured to the platform underside, and generously sealed against water penetration with sikaflex, to prevent any water ingress from the chain locker to the V-berth.
Have had no problems ever since, but ensure flushing of windlass with fresh water after every outing, including of course anchor and chain.