Several times now my Apple watch is stopping with low battery after a run with Strava. 

I record my 50 min run in my watch (series 6) with battery on ~50%.

Soming back home, before I can synchronize the run, the watch suddenly turns off due to low battery power. 
If I can manage to synchronize the run immediately as I get home, the battery level remains OK.

Also the recharging, getting back to live takes longer  and it drains the battery down immediately as long the run ist not synched. After synching everything is back to normal. 

Any idea how to solve this issue?