Pixhawk 2.1 false Battery failsafe

I am using 2 self made battery packs of 10,000 mAh, 6s (22.2V) with EMAX 35Aopto oneshot ESCs and tarot martin 4008 motors to power my hexacopter. I have set the battery failsafe at 22.5V, but only after 30 seconds of flight it goes into battery failsafe auto-land. I checked the battery voltage which showed 23.9V. Could someone tell me why it is going into failsafe mode and how to prevent this?

check the battery voltage during usage, like with a load of 10-15 amps, maybe you have a couple of bad cells in a parallel so your voltage drops when under load.

Check what image is set to. One way it uses battery voltage and the other is sag compensated. I use to get Battery failsafe when I was using the regular battery voltage. Once I turned it to sag compensated it was much more reliable. It still gave me Failsafe. But it was far more stable.