Trip from North Birmingham to Cambridge today for a meeting at 10am, left at 8am and Sat Nav told me 93 mile and 3 hours to get there??? Not intent on travelling at 31mph on the M6 and A14 I set off and still managed to get there in 2 hours.

On the way back got on the A14 and strangely the Sat Nav was telling to get off on every single slipway that I approached. After about 10 minutes got a local radio travel report that the A14 was closed westbound so presumably the Sat Nav had picked up the closure (that was about 20 mile ahead) and was diverting me a different way - clever old thing! Just wish it had explained why it was doing it coz my old BMW used to send me off dual carriageways only to rejoin them again!! Now - 2017 BMW X3 M Sport Carbon Black
Gone - 2014 BMW X3 M Sport Space Grey, faultless!
Gone - 2011 Freelander 2 SD4 HSE Bali Blue with xenons
Gone - 2008 Freelander 2 TD4 HSE Rimini Red with bodykit

Normally 'congestion ahead' type message flashes up with a yes or no option.
Worked on mine last week when the M25 was shut for a change! 09 FL2 HSE auto Lago Grey
71 Triumph Stag 3L
68 NGTCV8 3.5L

You may have it set to automatic reroute

maybe check the settings I have mine on manual so I can curse myself when stuck in traffic  Former Mod/Member, with the most post & Chicken George Arch nemesis