As a follow-up (and I had some time), I checked the Xcontroller schematic. It looks like they’ve kept the pin mapping the same between the Arduino Uno and the Xcontroller PCB so you maintain that code portability which also keeps it aligned with GRBL itself. The comment on the release page of “This is the official Grbl 1.0c for Inventables X-Carve using X-Controller.” and no mention of the Arduino/gShield combo made me wonder.
Phil: When you flash the Arduino, is your first step always loading ALL of your previous GRBL settings? The setting for $10 may be causing your issue. 1.0c changes the effects of $10 and, per previous posts, this is how they track Probing in Easel. If you pare down your GRBL settings that you load to the ones of “value” (calibration settings), it may work a lot better for you. Just another thought.