This one: ATR lighting bugs - #5 by SebastianJ7210 (that’s my post with the screenshot)
To check if it’s there, set time to night (midnight, just to be sure there’s no ambient light), and start cold and dark.
If the cockpit has some sort of lighting coming from an undefined source, there’s the bug. If it’s fixed, cockpit should be pitch dark until power on.
It makes night flying very difficult because the bug interacts with the other bug about exaggerated cockpit reflections ( Excessive reflections, glare, tint & opacity - canopy ) so you barely see outside