Another thing occurred to me on my run today: GPS is pretty sensitive to EMF interference. Riding under poorly shielded electric lines will send it wacky (you won't notice it if your wheel sensor is working); we had a car once that DH's standalone GPS wouldn't work when the CD player was running, even that little electric motor was enough to obliterate the signal. So I wouldn't be surprised at all if your DH's e-assist is interfering with at least his GPS and possibly yours as well. Besides the "usual" minor inaccuracies and occasional days when the government turns the GPS accuracy down (yep, they do that), that everyone has mentioned here.