My GPD win 2 won´t charge more than 85%

Hi, I´m having problems with the battery of my gpd win 2 pre 1st June batch, it won´t charge more than 85%, I let it charging 20hs.
I don´t know if it is a windows calibration issue or if it is a bug in the bios.
I already tried to calibrate it by letting it discharge to 5% and then let it fully charge (85% in my case),
Some times when charging windows reports the remaining time until 100% but some times no, but always reaches 85 and stays there no matter how much I leave it plugged.
I also disconnect and reconnect the battery and the problem persist.
Also I installed the newest firmware and nothing same problem.

I also have the original gpd win and I remember that with the bios it came form the factory it never shows the charging light until I flash the unlocked bios, after that it shows the charging light and turns off when complete.

Any advice is much appreciated.
Thanks in advance.

Send an email to kendyz@gpd.hk

have you install any Management software，if so, please check on your energy software，battery maintenance, longest battery life