Ok, we have tested today with another 3G operator and connection was stable.
We have two operators:
- UA-KYIVSTAR - problematic one
- MTS UKR - another one (alternative operator). With this operator, we were not able to reproduce the issue.
While sim card with UA-KYIVSTAR operator was installed, the 3G connection was intermittent and eventually got disconnected.
The video when the device had no connectivity is here. The logread file is here and troubleshoot file can be found here.
Once the connection was dropped, we waited for 10 minutes and but it was not recovered. We then changed the sim card from UA-KYIVSTAR > MTS UKR and 3G immediately recovered. The sim was changed at around 18:45 (if you check logread file). My friend also uses UA-KYIVSTAR on his phone and 3G connection always stable. I guess it is a sim card issue, but l cannot verify this due to the sim card size (iPhone does not support it).