M2GO-HD Laggy Faders

Hello,
Since our upgrade to 4.6, Our M2GO-HD has developed really laggy faders when using more then 2 faders. And since we use Key Lights for our stage we usually use about 4 at once to fade 4 lights down at the same time and all the lights cut from 100 to 70, 40, 0 with no fade. Just to clarify its not a cuelist, override or anything that wont allow fade. Its just a submaster. The fade works when using 1 or 2 but more then that it becomes really laggy. Is there any type of firmware upgrade for the desk only? We are now using 4.8 and its still really bad

Thanks
Josh