similar thing happened to me - i drove at 70 on a road because the satnav had a 70 in a red circle in the corner - i just assumed it was correct - as you would expect - i got a ticket and whilst i was a bit irked, i hadnt updated it for a while, so i just paid up, because regardless of reason i was still speeding.
i would be angry too if i regularly paid for updates and this info was wrong though ... however ultimately its my responsibilty to check.
its correct now so must have been a recent change.
incidentally the photo of me on the road showed a few large lorries to my left which is possibly why missed the 60 sign at that moment
it did teach me not to rely on the satnavs speed limit info though.