Those aren't errors in the GPS, but the data it's working with.
I'm curious what you'd rank as an 'error in the GPS'. I completely glossed over other classes of 'error'; such as the GPS guessing which way you are facing on a road when you start a trip so you drive six feet and then it recalculates a new route based on the fact that you are going the other direction but that's just 'bad data too'. Or then there are the times its positional reckoning is off -- so it tells you to turn but you are actually a block away from where it thinks you are but that's just 'bad data' too.
Are those errors in the GPS, Or in the data its working from...it seems to be a distiction without a difference to me.
We validate what the GPS is telling us to do, but we don't ignore it's instructions and plan our own path. If one can't turn left, they pass the turn and wait for the GPS to figure things out.
As often as not, it simply reroutes you around the block back to the same intersection you couldn't use the first time. If you are lucky it'll at least have you approach it from a new angle so you can legally turn... i've been unlucky on many occasions. And if the road is simply closed for construction or something you are boned when it does that.
If you can't get in the correct lane in time, again, no panic, just keep driving until the GPS recalculates.
Yeah, that's usually where the GPS starts insisting you make illegal U-turns at major intersections, or emergency vehicle access roads, etc...