No, I didn't do compass calibration. But the very same drone with no payload behaves as expected. 7 satellites locked.

Since it's a prebuilt copter I didn't try modding PID values but in fact I've no idea if the settings have been tampered with.

Hi,

I grabbed a good deal on a used xFold Travel X8 octocopter. The specs look promising and I was eager to finally fly my Canon R5. Total payload weight is around 3kg - well within the envelope. Empty copter weight is 5kg. Batteries add another 1.5kg. T-Motor MN4012 340kV motors with 15x5 props. DJI Naza M v.2 flight controller. The batteries are two new 6S 12Ah packs.

When I fly the drone with no payload it behaves as expected but when I add a payload I have the following weird behavior: when battery discharges to around 23V the copter has a tendency to land in GPS Attitude mode and no stick input (throttle @ middle). If I push it by moving the throttle stick up it holds altitude but some time later it starts rotating in yaw/horizontal plane. I couldn't see a failing motor though.

Any ideas?

I have several theories I'm not disclosing to avoid confirmation bias.