RE: Core One crash/restart
I had this issue as well. when the printer goes from rear right side to front left side, I notised that the left rear motor moves but the other one almost stay still, when the printer restarted like a power cut. Grounded the left rear motor, problem solved. I fastend a cabel on one screw that fastend the motor. and other side a random spot on the frame
RE: Core One crash/restart
I added the star washers to both my X and Y axis motor, verified I have continuity from the frame to each motor with a Fluke Voltmeter. I have been printing for over 10 days without the issue popping up.
RE: Core One crash/restart
I had two prints fail this weekend with a ton of travel and crashing. While I wait for my 3mm washers to arrive I cut a test lead up and that same print ran last night without issue. Seems like the answer. I’m going to set up my o-scope and try to measure this someday. 
RE: Core One crash/restart
I had two prints fail this weekend with a ton of travel and crashing. While I wait for my 3mm washers to arrive I cut a test lead up and that same print ran last night without issue. Seems like the answer. I’m going to set up my o-scope and try to measure this someday.
In my case I just scraped away some powder coating from around the screw hole. That was enough to get a decent ground connection.