Well actually mine is an eBay cheapie ‘truckers’ satnav. Going along the M6 southbound the other day heading to West Bromwich, it tells me to come off at junction 10 Walsall. Now this is a local(ish) area for me, but ok thought the satnav knows a better way. Come up to the motorway island and the satnav tells me to take the second exit, looked up at the screen and yep it was telling me to rejoin the M6 southbound. Effectively I had leapfrogged the stationery traffic and was further forward on my travels. Is this the worlds most intelligent satnav? 
Yep we all know it was probably a technical glitch, either that or the spirit guide of a lost Chinese warrior full of wisdom, has become trapped in the case during manufacture. 
My old Tom Tom did this, was the road realigned?
Dont mean to ■■■■ on the sat navs parade and grass it in but it told you to do that because coming off the slip road and rejoining was probably technically the shortest way. My old sat nav when coming towards Glasgow on the A737 told me to take the exit for Greenock but go straight at the roundabout and then rejoin the M8. Probably shorter by about 3 feet but adds ten minutes due to the traffic lights! 
In deepest darkest Ross on Wye this week and I foolishly trusted the sat nav for the last three miles took me through the town which isn’t the most artic friendly. So on arrival I asked the bloke best way back to A40. Turn right out of the farm follow the lane and turn next main right turn. So off I set with the sat nav on out of interest. It tried to turn me left down every track and lane.
Tis work of the devil. Lazy on my part. No more
Have to agree about the eBay cheapie sat navs. More intelligent than you may think.
Every time I went to Swindon truck stop, it kept telling me that I shouldn’t really be here and should leave the area at once.
How right it is!
I hated it when my old satnav told me to turn around. Was a bit pointless, as all I could see was the drivers seat and the back of the cab. 
Getting back to satnavs, problem I have found is realistically you have a choice of fast route or short route (or their derivatives). Garmin are also now offering an eco route option, that probably takes you to the nearest cycle shop?? Am never quite sure whether to go with fast or short route when using a satnav. Even things like traffic calming measures with chicanes, parked cars at school kick out time, or even overhanging branches, can turn a suitable road into a very unsuitable road for trucks. 