Weird Altimeter behavior during cycling (bug?)

I recently bought an Enduro 2 and i have weird/clearly wrong elevation data when recording a cycling activity:

This it the elevation graph of my commute home from work, the watch records between 50-80m of elevation gain when it really should be 12m.

It is clear that the altimeter records some weird drops only to correct itself a few seconds later. It is worth noting that everything seems to be fine during running activities. Also my Forerunner 955 always showed me the correct elevation gain. Anybody with an idea whats going on here? 

(i tried calibration before starting the recording, same issue) 

-Software Version 13.22