RC4WD Big Offroader servo issue

[500swmag]

I've been messing around with a RC4WD Big Offroader radio for a few weeks now and I seem to be having some sort of issue with my servos and was hoping for some help.
It seems certain servos won't work in channels 1 or 2 but will work in the 3rd channel, so far it has made converting my fleet over quite difficult as I am running out of servos to use for the steering.
Am I the only one having this issue or are others experiencing this also.

I am using a futaba mc330cr and RC4WD mayhem servo (this works) in one truck.

The other is a duratrax 16T esc and a towerpro MG995 (doesn't work)

it seems towerpro servo won't work on channels 1 or 2.

any ideas (digital?)

Thanks.
-500