Set time resets itself regulary to minus 2 hours

Hello all,
i am new here in this forum. I received my bangle.js a few days ago and i am experiencing a strange problem which looks like the set time resets itself by minus 2 hours after some time.

This is how i can reproduce it:

1. Set time to local (MEST) time (e.g. 10:00) via the settings menu on the watch
   
2. Go back to clock / home
   
3. Do other stuff besides looking at the watch (it goes to sleep)
   
4. After some minutes when i wake up the watch and it shows me 9:00
   
5. When i go to settings to set the time it shoes me Hour: 8 (yes 8, not 9!), Minutes: 0, ...
   
6. When i now leave the settings without setting the time the clock on the home screen shows me 8:00 as the current time
   
   

This happens every time i set the time.
I am using Gadgetbridge and i tried both setting "synchronize time" enabled and disabled - no difference here.
My bangle.js has Version 2v05 with bootloader v0.12, launcher v.01 and settings v0.07.

I don't know if i am doing something wrong and how i can provide some logs or help debugging this bug.