Hey I just spoke with our engineers and wanted to provide some clarity about what is going on:
The spindle is powered by a variable frequency drive (VFD), and it is common for VFDs to generate some current that flows to ground due to the high frequencies and capacitive coupling between current carrying conductors and grounded elements. This ground current can generate nuisance tripping of the GFI since it creates an imbalance between the current on the hot and neutral lines. The X-Carve Pro was not designed to operate with GFI outlets and is functioning as intended. Do not modify or open the controller as this could cause a safety hazard.
We recommend plugging your X-Carve Pro into the nearest non-GFI outlet to avoid this issue.
Sorry about any confusion surrounding GFI and the XCP in general. Let me know if you’ve got any other questions!