Regarding #1 … are you printing from a computer (USB connection) or via the USB stick?
This makes me wonder if you were printing from a computer and it stopped sending data … or printing from a memory stick that is having issues. If using Cura LulzBot Edition to print, you can go into the “Console” to check for messages as it prints (or even send a command to see it will respond.)
Regarding #2 … the machine uses mechanical end-stop switches at the top of the gantry tower (there are two… one on the left and one on the right side). X and Y axis do not use physical switches, they use “bump sense”. The board is able to determine how much amperage the motors need to move and this provides a way to determine when a motor has reached the end of travel. The “bump sense” is a tunable value in the advanced settings.
Is there any possibility that the “shaking and chaos” (typically the noises made as the motors fight to move the belts when the print head is already at the travel limit) could be coming from the X-axis motor and not the Z axis motors?
I ask because, if it were on the Z axis … I’d expect a wire fault to break and just stay broken until repaired. I wouldn’t expect intermittent issues. But on the X axis that uses bump-sense… I can see how it could be intermittent.
My Workhorse had an issue with a broken wire on the X-axis (the Workhorse uses a mechanical switch … not bump-sense). I found it by using an ohm-meter to test the continuity.