This is a long standing issue that has affected a lot of units if the forum is anything to go by. It's affected my long rides, and I also get ridiculous speeds of 400mph showing! I logged it with Wahoo and they asked for access to files and I then heard nothing more. Wahoo claimed to have fixed it in the last firmware update, but feedback is showing they've fudged it by deprecating the gps accuracy hugely, and the issue still remains. That said I did a 5 hour ride at the weekend with no issues. I have to say their ability to fix long standing bugs, even minor ones, is turning out to be no better than Gamin's. My unit is still afflicted with the mixed units randomly resetting from miles to kilometres, even when riding, which again has been going on forever and drives me nuts.