Ax1500 acting uncontrollably

I have an ax1500 controlling 2 motors in RC mode. Recently, it did not respond at all, then worked ok for a while, then started acting strange: it spins both motors in forwards then rev, fast then slow, etc. It does not respond to the rc radio at all. Does this sound like a controller problem or radio problem? (radio is a spectrum dx6i)
Btw, I checked the radio, at its operates a servo.
Thanks!