I have built the same drone for some time a Tarot 650 with Pixhawk and now using the Radiolink pixhawk. I use the Scotty F. build for telemetry and have stayed with 3.2.1 for that reason it has worked and flown smooth. This time I cannot find why the motors pulse even at low speed on the ground in stabilized mode and loiter in the air. WhenI bypass the FC they run smooth, I changed to an original well tuned Pixhawk and it does the same. I have reviewed the logs as well as I know how and nothing. I am thinking the information for throttle passes thru the FC to the ESC is corrupted yet I cannot determine where or why. Has Qbrain changed their ESCs? i have tried two with the same issue. My other thought is the firmware it came loaded with has corrupted the firmware, I reset to default even loaded old firmwares and built back to 3.2.1 still didn’t work. If you can help please let me know I have tried all i know.
I solved this issue. the new Radiolink pixhawk did not load the ESC calibration thru the FC like the 3DR pixhawk always has. For some reason it seemed to calibrate correctly but when in flight modes wold pulse. I reloaded everything and did a manual ESC calibration before connecting the pixhawk and everything works correctly.