cogging noise on the mamba max 9xl setup

Hey guys been running my setup and its been running smoothly except today ive been hearing these cogging kinda of noise. i really dont know where its coming from. my friend told it could be the sound of my dogbones hitting the cupand told me to put some kind of foam to stop the noise. what do u guys think? oh by the way tried my setup on 2x 2s 4000mah 7.4v lipo and its wicked compared to my 2x 6cell 3300mah 7.2v nimh. what a big diff it makes. Also having some problem tried speed testing it front of my hse and it would go on brakes for half a second without me braking. do u think its some kinda of interferance? do u think its the ubec?