I received a new BV9000Pro and when it is not used (screen is turned off) then after few minutes it simply turns off whole mobile automatically. I can start it with power button again, but it is really annoying. Have you heard of a similar problem?

More info:
- I have latest ROM: BV900Pro-FHD-VO.6-20180104    (Also tried to flash older one, but problem remains)
- Tried Factory reset
- When mobile is on charger then it did't happen. Mobile stayed turned on whole night.
- Battery indicator in top right corner shows weird values of battery life. For example it shows 100% but when mobile is restarted then it shows 64% and even when i put it on charger for few hours the battery level stays at 64%.

For me it seems like problem with battery. Do you think that changing battery can solve this issue, or is something else?

Yes, a bad battery seems to be the culprit.