David,
Please check your dust hose ground one more time. The symptoms you list point at ungrounded high voltage static. You cannot use the same ground as the control box, as it may cause a ground loop issue. Below is the suggested 'tried & true' method of correctly grounding your dust collection system. Take NOTHING for granted...
First, verify ground between electrical system ground and your dust collector chassis. Put one probe of meter in ground in electrical outlet & other probe against a metal bolt, screw or lug on the DC chassis - preferably the exact location you plan on grounding the end of the bare copper wire. The spiral bound wire encapsulated in the hose is not suitable for grounding. It is there for physical support only. The ground must be a bare copper wire without exception. Doorbell wire stripped of insulation works perfectly.
Run the bare copper wire through the dust foot, connecting to the alligator clip, then through the entire length of hose, then go through the hose and tie off at the place where you checked continuity. You can tie a rag to the wire, fire up the DC and throttle it until it get close to the DC, before turning it off. Then test continuity between the copper wire and your electrical ground.
The high voltage generated by dust collection can, will & does overpower low voltage DC switches and sensors on the machine, that operate at 5vdc (USB, input switches) and 24vdc (prox switches). If you don't give the voltage a 'path of least resistance' via bare copper wire inside the hose that acts like an antenna to wick up the static - then, it will find it's own path, which will either be the X or Y Prox switch wires (long antenna) or USB cable (long antenna)...Prox switches that get 'stepped on' via high voltage result in false 'Limit Switch Hit' and 'Emergency Stop Hit' messages, interruptions in the communication stream or 'thuds & bumps' in movement are caused by the USB 5v cable getting 'stepped on'. If you have good Com speeds, and computer is good...you've got static issues.
For the heck of it...check it again. AND - also check that you have continuity between the dust foot clip and the dust collector. Wires CAN break!
I've seen it happen so many times that people think they are grounded, only to find they are not because of a broken wire, a corroded contact or other thing that doesn't work properly.
-B