Well, just as an experiment, I removed the extruders from the carriage, and hung them over the top of the machine, near the door to the enclosure (with the enclosure top removed) and ran a test part program, just allowing the filament to extrude freely into a coil in front of the machine. It ran the entire program with zero issues. This confirms that it is in fact a wiring issue related to the movement of the print head. My assumption is that there is either a short in a wire, or the plug connector behind the extruder stepper motor has a poor connection. I smeared some dielectric grease on the plug, and I secured the wire loom to the filament feed tubes with zip ties. Will now run the same small test program to see how it does.