When you say the motor keeps moving after you turn off the transmitter, it could be to do with the failsafes set on the receiver. But if it works just fine now, there's no reason to mess with it.
It probably is something to do with the failsafes in the controller, I had this problem at Grantham as well with a different set of speed controllers. Calibrating it should rectify it so I am not too worried at this stage and as you say, it appears to be working fine, I'll leave it alone for the time being.