I've done more testing on the electronizes, it seems when the motor stops one of the relays clicks. It is not just failsafing but either actively breaking or even trying to reverse the motor. It still happens with a different motor (14.4v) and with different radio gear. It happens when I run it on one 3s lipo as well as on 2 (giving 6s) but appears to be less severe and only happen on one motor whilst on 3s