Erratic Movement

I have been having strange behavior from my ShopBot lately. I would like help figuring out if it all stems from one primary failure or possibly multiple things gone wrong. Here's what we know:

1. Three weeks ago, we began having random losses of power to the ShopBot. It would shut off (I know it shut off because I could hear the motor or spindle stop mid-job). A minute or two later, it would come back on. (No one touched the power switch)

2. We were able to run cut files without issues, as long as the power didn't cut off in the middle of a job.

3. One week ago, we start up the machine and begin moving it for positioning a job and we start getting hard stops and jerky movements.

4. Today, the random power failures have stopped. We decided to upgrade the control software and firmware. Restarted the computer and ShopBot, however, we still get the jerky movements.

5. The diagnostic report shows different times for the Packet_ET. The highest was 45.5ms and the lowest was 6ms. I guess this corresponds to the sometimes smooth and sometimes jerky movements of the machine

Things to know to help diagnose:

-I don't think it is the motor itself because the jerky movement happens in all axes and is random. (will move smoothly between periods of jerky movement) The problem persists regardless of direction of movement (3 axis) or speed.

-We have a dedicated computer. We have a new USB Hub. But we have not checked any electrical connections yet. Our fabrication lab - and obviously, the ShopBot - are located inside of another facility that has all types of medical equipment and a cafe and stores. The grounding was done my contractors hired by the building administration.

Questions:
1. Does this seem like one issue or multiple issues? Electrical, Communication, other?
2. Could our equipment be affected by other equipment wired into the building?
3. How can we narrow down the source of the problem.

I can add pictures or video if it helps. We have a prsalpha and we only use it less than 10 days out of a month, and it is 4-5 years old.