QGC drone battery percentage differs by flight modes

I am using Qgroundcontrol Development version with a custom px4 firmware for the Pixhawk Cube.
Few days ago, I realized that the battery percentage is different base on the drone’s flight modes.
I am using 4 cell battery and the parameter is set as 4.2V for Full and 3.3V for empty battery.
The Voltage divider is set and the Qgroundcontrol shows the actual battery voltage.

However, when I switch it from manual mode to position mode, the voltage stays the same but the percentage goes slightly up.
When I change it the offboard mode, the percentage goes even higher than the position mode.

Is this a common thing that anyone has experienced or is there something wrong with my setting?

Does anyone has an answer?