I actually wouldn’t mind if someone else quickly chimed in on this, because I forget what the exact reasoning was and I’m heads down on building stuff for my daughter’s birthday party… Maybe @RichCournoyer can shed some light? In short, I thought it had to do with an incompatibility with G54. Setting it to 1 is what I’ve had to do with this workflow:
Fusion 360 --> Grbl Post Processor from @Strooom --> Universal Gcode Sender
This is partly how I ultimately stopped my machine from flying off to the far right corner like it has for you. I still occasionally have to edit the headers for my files to make sure they don’t do anything stupid, including Z retracting and hitting the limit switch.
(As @mikep mentioned above, Strooom PP: A better Fusion360 - GRBL PostProcessor)