Fenix 5 Plus - Speed/Distance goes crazy after 40/50kms or 8-10 hrs of activity?

Former Member
Former Member

G'day, 

I have been using my Fenix 5+ problem free for trail running/racing since they came out but have started to experience a reoccurring problem on longer races (50+ km). I mainly just use a single screen showing distance and average speed in km/hr and have auto lap turned on. The data recorded is accurate against known points on the course (markers, checkpoints etc) until somewhere around the 45km mark and then all of a sudden the auto lap vibration will start going off every minute or less and the watch will show me running at 60 or even 90 km/hr!

This has happened on a number of different occasions over the last year.  I immediately stop the activity, save it and then start a new activity which seems to fix the problem until I again get up to 40/50 km.

I've tried turning off auto lap, vibration, GPS/Glonass and GPS only.  I've also tried ignoring it for a while to see if it comes right, which it doesn't. There doesn't seem to be any other issues with the watch other than all of a sudden thinking I've attached rockets to my heels.

Has anyone else experienced this?