Anchor windlasses are by default installed in the most harsh and exposed of all boat locations. They have to continually tolerate serious saltwater over it on a frequent basis. Anything you can do to protect them will pay dividends in terms of limiting failures and problems. I always have a canvas cover made and keep it covered at all times to reduce the effects of weather, so much damage gets done on a passage with water constantly over the bows. You need to make sure that you can really tie down the cover though. Another precaution is to remove and lubricate all bolts on the windlass so you can actually get them off at some future point. Many casings of anchor windlasses are made of casting and corrosion is very common.
Always wash the unit down anchor windlasses in fresh water to reduce corrosion. Where there is an oil sump, check it for correct level, and also check oil for water contamination. I am a bit pedantic and try and change oil every year so its always clean and gives optimum lubrication but that is just me. Where there are grease points pump in some grease and expel the old. Do this every 3 months or in accordance with how much use you are giving the windlass. Things that are operated frequently tend to do better than equipment that sits for months on end. Try and run the anchor down and up a few times so that the motor warms up, as windings may absorb moisture and this is a good way of drying things out. As well carbon brushes which are spring loaded anyway tend to be freed up and move properly and maintain correct commutator to brush pressures.
Mechanical problems are common, mainly it is caused by the chain jamming in the gypsy, or a poor angle or offset causing the chain not to lead in properly. Sometimes people just choose to live with these issues but there is always a solution. Bow rollers are also a common problem, and they should be checked for jamming also. More than once has a chain stopper been left engaged and power applied, severely stressing the fitting. Another common problem area is where the chain is not coming off the gypsy and falling down the hawse pipe, the chain heaps up and when tension comes off the chain the slack chain also jams. As discussed elsewhere it is important to check that chain falls properly and doesn’t pile up. About anchor windlasses and about anchor handling.