OK, Y moves when I push in the DER manually. Not sure why - I dont know if the machine is trying to home or something else. If I restart Mach 3, does it 'forget' what it was told before?

Glad ive got movement, not sure whats impacting DER relay yet. It was the door latch, thats sorted, something else is now holding it out. Looking to try and reverse the direction, where is the 'jog wheel' in Mach 3? Ive seen a pic of one, is it a plugin?