Strange green material reflections in Editor Mode

Have a simple scene set up with a single HDRI. My project was previewing correctly in Editor mode but for some reason I am now getting a strange green reflection off the midtones. In Play mode it looks correct.
Just from the attached pictures can any experienced UE devs suggest a possible cause for this? I’ve tried rebaking several times.
I’ve also set my ‘Show’ menu back to defaults.