First flight test - several power issues - please help

I went to flight test my hexacopter for the first time and had several power issues. They may or may not be related so I have included both issues in one post.

Issue 1 - Uneven throttle response across motors.

I armed the hexacopter in manual mode (without props) and throttled up. The motors started spinning at different times and while they were spinning some of them would stop. On throttle down some would stop before others. This was not a little gap between the first stopping and the last, they were definitely not ‘in-sync’.

I did a motor test in the actuator tab, and when I control the motors from QGroundControl, they spin up and down together perfectly.

Issue 2 - battery failsafe activating on full battery

The battery failsafe activated several times, either saying low or critical level had been reached, or the battery had been disconnected despite their being a full battery, and the status bar icon showing a full battery. See attached pic.

My setup is:
Flight controller : Pixhawk 6C mini
Autopilot : PX4 (latest one that QGroundControl added)
Power module : Holybro PM08
Receiver : Radiomaster R86
Transmitter module : FrSky ACCST

Battery failsafe parameters:
Low : 20% - RTL
Critical : 10% - Land

Any advice on how to proceed would be very helpful. Thank you.

I have a few suggestions but assuming all cables are connected properly, would you be have access to a multi-meter? Hooking this up and doing a sanity check would be my recommendation. I will mention, upon looking this module up, can you double check the instructions here?

Thanks for the response
I followed those instructions for the power module and the parameters are cprect.

I resolved the uneven throttle response by fine-tuning the PWM values in the Actuators tab.

But I am still getting battery failsafe activations due to the critical level or warning level being met and QGroundcontrol saying battery is disconnected, despite there being a full battery.

I did test tested the set up with a multi-meter when I was building it but if you can suggest something specific to test that would be great.

So I’d hook up the multimeter to the power entering the flight stack, followed by throttling your motors (WITH PROPS OFF) and basing any of your findings to determine further actions.

( I’m also new to helping via the forum but wanted to contribute in any to the community. )

Best of luck!