Turns out that 3c and 3d are not reversed when splitting the right shift in the way that the Mark I layout does. Reversing it here, rather than in the generic satan.h to avoid breaking the other layouts.
Satan GH60
Keyboard Maintainer: QMK Community Hardware Supported: Satan GH60 PCB Hardware Availability: https://1upkeyboards.com/gh60-satan-pcb.html
Make example for this keyboard (after setting up your build environment):
make satan-default
See build environment setup then the make instructions for more information.