I know 3 boats lost thru wind vanes and only 2 were solo.
Yes, its a wind shift problem... and one of the examples hass appeared in the next post to yours!
I dont have a back-up my Raymarine (ex charter boat so its done lots of miles) has had 35,000nms trouble free except for a small spot just north of Bahamas where it started playing up and I had to hand steer for a bit. Funnily enough the error occured again at the same latitude in the ICW 6 months later!
My back up would be to hand steer and hove to when tired. On a long passage it wouldnt be fun... but it would be a bit charter building.
Always great to hear opinions from sailors like yourself who are out there doing it!
I have had a similarly positive experience with my below-decks B&G. In fact, I have an excellent dealer who has helped me learn the finer points of the system, and he consistently talks me out of spending lots of money on spare parts! Like a windvane, balancing the sail plan is essential, esp. for conserving amperage. When appropriate (fully awake near shore or far offshore w/alarms), I can also set it to steer off the wind like a windvane and not have to fuss with sail trim. This is particularly helpful when tacking upwind. I agree that it steers much better than I can on any point of sail.
I am nonetheless more positive than you about windvanes, but this is only from what I read & hear vs. actual experience. B'twn cost, installation, and having a larger, center cockpit boat, I have been reluctant to conclude that it is the way to go for me. FWIW, there's a wheel pilot made by CPT that is reputed to be the only one robust enough for larger, heavier boats. It costs about $2,000 and can be stowed in a small case unless needed for emergency backup.
I must confess to some paranoia after reading so many internet posts about AP failures & the ubiquitous "Mr. Murphy". This is thus far contrary to my own experience with my AP and apparently yours as well.
Thanks again for chiming in.