At 50 % voltage was 3.7 volts. At 15 % to 0% one cell dropped to 3.2 volts and then it showed weak battery warning.
I rotated them and same happend, same battery, different slot.
It turns out all 3 batteries were bad. They were purchased in shop with mod as brand new but they were from old stock. Code on all batteries reads they were made in 2015.