I noticed the relative terrain display disappears when on ground. I think this is the same bug which plagues every MSFS aircraft. The TAWS / GPWS system should be inhibited on ground, the terrain display system should remain active however.
The G1000 NXi, like all default MSFS aircraft suffers from this weird autopilot roll axis bug where the AP steers opposite when giving manual roll input e.g. when steering to the left the in-sim yoke can be seen moving to the right by the autopilot. The ailerons are following the joystick however so the in-sim yoke which is driven in opposite direction to the control input is a dumm.y with nothing attached to it.