I ran into a lighting bug in the fourth region. I was controlling a character using the Voidlight passive as my light source and another party member was equipped with a Laser Greatsword. Whenever I was in a pitch-black room the light source would alternate between that of my Voidlight and the much weaker light of the Laser Greatsword as I moved around, leaving me with nothing but the faint glow from the laser about 50% of the time. This occurred during the run in which I first encountered the giant eye monster so I have no clue if that had something to do with it, but I haven't been able to replicate this issue on future runs and I don't remember any other information.