2012 JD 329D will start but no hydraulics and won’t move

Trying to track down why this keeps happening every couple of months. Machine will start, but then hydraulics won't work and wont move. When this happens i call the local service dealer and they come out and reset the computer to the controls and it seems to work for a while. Costs $400 each time and i've had it done 5 times over the course of a year and a half. They aren't sure why it keeps happening. Any suggestions? Short somewhere? Thanks