Mine did the sames tihing sometimes, stearing obeai but not the controller. I simply switch the controler off and on again, and this is OK.
And for the poor performance with the MGM, don't worry, MGM have a very bad configuration for the LVC.
I run mine on Race mode to obtain decent performance, but you should be carfull, because on race mode, you don't have any protection for your li-po.

I realy don't like MGM and i'll order a MMM soon