Honestly we at the dealer level don't really know for sure the exact internal problem within the unit as whatever's the specific cause, it's electrical and even though I've taken one apart to look myself, there's nothing that's obvious visably. The Vadis PC usually picks up one or more codes for it stating nothing more than "internal fault" and at that point, no more repairs short of replacing the complete assembly can be done. I'm sure that engineers know the exact cause but I havent heard it spoken yet so I won't guess.
It's not a simple throttle base as they once were a couple years ago when a throttle cable was what opened the throttle plate, instead it's a very complicated electric motor that gets all its info from the fuel ECU (two way communication really).
Replacing the unit cures the problem and hopefully the new part is better than the original.

....and yes, MAF meters are also fairly common.