DIY anamorphic | How do ND filters affect flares?

A video showcasing how different ND filters (Hoya Pro ND and Tiffen Variable ND) affect flares in DIY anamorphic solutions. Camera: Panasonic S1, recording in V-Log Lens: Nikon 100 mm f/2.8 Series E @ f/2.8 Schneider Cinelux ES I’m not really sure what’s with the diagonal flare which appeared in ND 16 shot. The filter itself is clean and has no scratches. Well..