I have a cforce 500 that works great except sometimes it won't disengage 4x4. Normally I can hear the switch from 4x2 to 4x4 but when I hit the button nothing happens. The last time this happened after about a hour of use it resolved itself but I'd like to know the reason behind it. Currently, it's stuck in 4x4 and I can't disengage it or lock the diffs. I don't hear the motor trying to even switch.