After some weeks of stepping back from programming, I decided to try and make a UI that will be compatible with OSX (10.10 to 10.13 as far as I know) so OSX simmers might try Mission-X plugin and maybe will add their own adventures.
To enable the UI Compatibility mode, you should tick the "Toggle UI" submenu in Mission-X menu and then restart X-Plane. This should be a one time thing. Main reason for this behavior is how NUKLEAR vs Compatibility mode handle bitmap images.
It seems that NUKLEAR library flip the images internally while the compatibility code needs to "tell" the loader to flip the image. So if you "tick" the "Toggle UI" submenu without restart, you should see images flipped.
Last, the compatible UI might not be as polished as I would like, but I hope to make it nicer in later versions.
Until next time
Have great simming