Garmin randomly misreporting speed? 28.34

I’m talking about the battery for the wheel sensor.  Some have a child proof coating that makes them taste bitter. If so, sometimes it causes a problem with sensors.  Wiping the battery with alcohol to remove the coating helps. 

I'll check, but no low battery alerts have come up. I would have thought the data fusion from GPS, Accelerometers and wheel speed sensors would mitigate against intermittent wheel speed sensor drop outs. Is it possible to validate this as the root cause, just clean battery with isopropyl and test?

felixrising everybody can send me pm here. your connect activity is set to private (but why i asked the FIT file because that contains extra infos about sensors, used source for speed in given second, etc).  or upload here https://www.file.io/  , it is free (just i wanted to avoid to share your full activity in public).

Sometimes it is the sensor, sliding on the hub. I find it happens with older sensors when the band stretches. A little piece of duct tape or double sided tape stops the sliding

the OP has Garmin Speed Sensor v2 (i dont think it is slipping, only one section is problematic, probably if he rides next time here there will be the same issue also) problem imho is a big metal structure (a barrier) on the left side of the road on this section.

There is a guard rail to separate the road from the pedestrians, and a body of water to the left too. 

Id have thought the speed sensor 2 (or internal IMU) would override any wonky GPS readings where surely multipath error stats and DOP worsening would degrade the preference for GPS for speed estimation. Maybe they're not doing any sensor fusion?

No IMU.  The speed sensor works by detecting the relatively rotating magnetic field of the earth.  This seems to almost always work, but there are rare situations where it gets flummoxed. 

I had the same issue. Didn’t have an issue after using it for 2 years. But turns out it was because of being in the rear wheel. Moved to front and no more issues