I suspect that is re-routing due to traffic information. It's not as good as TomTom but knows about the worst stuff.
I did think it was something to do with that dbm, but on a few occasions it has tried to make me come off the motorway, I have ignored it, carried on and I found nothing on the way, totally clear road.
On sunday night coming back from Liverpool it said to come off at a junction and we ended up coming back from Southport
way !!! Starting to think to get the my old TomTom out....