Check the crimps or solder connections on the contact tips for the battery connector on the machine side (the heavy cable connections where the battery plugs in on the machine). Check your B+ wires for loose connections. Do the same for the negative side.

When the whole machine shuts down like that, it's usually either a battery running down real low or a bad/loose connection in the machine itself. I don't know your machine offhand but these are the things I would check initially if I got a call for something similar. Check relays and contactors too. It could be in a controller too.

I had a Yale pallet jack (MPE060LEN/A896) a few months ago that would code out with "the tiller arm is in the down position when the key was switched on" even though the guy was just driving it. I think it was a code 32, can't remember the code offhand. Found the solder connections in the SB plug were bad. I always prefer crimping them myself.