Unable to start ESC calibration

I have PX4 FMU v2.x with 1.10.1 firmware. I calibrated everything except ESC calibration.
When I click Calibrate at Power>ESC PWM Calibration. It says “Transition denied: SHUTDOWN to INIT”
As I understood it means SHUTDOWN mode is activated, because no battery connected, but ESC calibration ask to dsiconnect battery from FC.

When I start FC with attached battery and usb connected and then disconnect battery it says:
Dangerously low battery! Shutting system down. System does not support shutdown".

That sounds like a firmware bug. You might want to post in a firmware forum or slack.