So this happened on one of my recent rolls. This is the ONLY frame that it happened to. It's an F5 with a brand new MF-28 back, I had exposure imprint enabled.
I've run about 10 rolls through this combo so far, and haven't had any issues except this. Any idea what could've happened? I'm hoping it won't happen again.
p.s. out of the entire roll, it had to perfectly ruin this one shot.
Flare. Looking at your image in PS inverted reveals no other useful information so my first impression stands. It might have been light entering the viewfinder eye opening that caused it. Nikon put the closable blind in for that purpose but shooting hand held makes it difficult to use.
Is your info being imprinted between frames? It looks to me like the LEDs fired into the image area either too early, while the exposed frame was just beginning to move, or fired too late, just the frame-to-be-exposed was coming into position.