Possible cogging ??

I've been having a problem with my brushless setup while trying to lift the nose while in the air to correct my landings. When I gas it, the motor momentarily stops or slows down before spinning again. As you can imagine, if I'm already needing to lift the nose and this happens, it causes some really ugly body first landings.

It's doesn't appear to do it all the time, but it only takes one time to break parts.

This has been a problem on several of my setups but it's to bad with 2WD. With the maxx it's terrible when it happens.

My setup is:
10L
9918
12 cells
16/70 gearing
controller's BEC
Response tires.

Anybody else have this issue and know how to fix it? Is it BEC related? The voltage shouldn't drop below the cutoff with 12 cells right?