My SkyHero Y6 with APM 2.5 and the latest stable FW makes strange "knocking" sounds when in idle. There are none of these sounds when working at higher throttle.
I use the Tiger Motors MT2814-11 710 kv and Yuki cayenne 40A Opto ESC (simonK).
The video is here:
Has anybody heard that before? Could this be an issue of the "teaching all ESC at once" method?