The seller dont accept returns. I still hope this is battery issue. I will full charge battery and test it again. My battery is in 100% charge and it is still charging for about 1:30 hrs. It is strange.
The seller told me:
The battery issue you describe is has happened to all Lenovo laptops I have worked with so far. It only happens sometimes when battery is running out of power.
Removing the battery and putting it back in resolves the problem and the laptop runs happy.
Buying a new battery at some point may help, but just like I said - the issue happens even with the newest Lenovo laptops.
ps: you are right it is not 15", but 15,4", pretty good resolution.