Not a regular AE-1 user (have an A-1) but have one inherited and offer a "thinking out loud."
You only show the image area -- what does the rebate area on the film look like?
If there is light struck area extending beyond the frame and in alignment with what's in the image, it's likely a light leak. And in the Ax-1 family, that door hinge seal is a likely candidate.
But -- the shutter is a focal plane that travels horizontally -- I speculate the pattern seen could at least be possible if there is something misbehaving in the shutter travel. In that case, the rebates should be clean. I think maybe the edges aren't square and clean enough to be from that cause, but it's worth a thought.
Light leaks are always interesting because they can be happening between the film gate and the supply or takeup spools/cassettes/whatever, as opposed to while a given bit of film is facing the lens. As such it can be tricky to determine when and where the problem is happening