@Alex-Kushleyev the tests were done all in succession with the same 4S (16V) battery. We are using Xing2 2205 2300kv motors with 5 inch props.
I followed the ESC calibration guide: https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/blob/master/voxl-esc-tools/calibration.md
I started with this parameter file: lumenier_2305_2400kv_GF_D90_4S.xml and modified it as follows:
param name="vbat_nominal_mv" value="15200"
param name="num_cycles_per_rev" value="7"
param name="min_rpm" value="3200"
param name="max_rpm" value="25000"
Then I uploaded these, and did the calibration. I got good results initially, and all motors were spinning up fine.
param name="pwm_vs_rpm_curve_a0" value="29.00369359"
param name="pwm_vs_rpm_curve_a1" value="0.414700099"
param name="pwm_vs_rpm_curve_a2" value="3.58E-06"
Nothing else was changed in the parameter file, and it was uploaded to the ESC.
But while the drone was on bench, after 2 or 3 times of running, the motor on ESC channel 2 stopped spinning. I tried re-calibrating but now even during the calibration that ESC channel does not spin up the motor.