Any electrical experts out there?

ScottG wrote:
A coil like in a motor, can trick a sensitive GFCI into thinking there's a ground fault. This is due to the rule of "ELI", where voltage always leads current through an inductor (or coil). Because of this, there is current flowing that doesn't follow the timing the GFCI expects. This is the differential current the rep spoke of.
This was a serious problem in the early days of GFCI's but they have generally been updated to solve the problem.

This sounds like a definite possibility. If so then not all motors act the same way. My ceiling fan works great as does my small shop vac. For now I'm going to have to assume it's something specific to the motor or coil in this vacuum unless and until I discover another a problem device.