Keyboard losing contact

I have an imac and I am running cubase 10 on Mojave. Since upgraded my M-audio 49e keyboard either looses contact or freezes any VST I run. Has anyone had the same problem and managed to solved this? Would be grateful for any links or help on the subject.

SOLVED. Ive just tried using the keyboard with an external 12v power supply and all is good! It would appear that the voltage on the USB cable is not enough.