This picture might not look like much, but it’s confirmation that I may have finally beaten my streaking issues. The solution was to not use the recommended depth of chemicals, as counter-intuitive as that sounds. The stated depth was 250ml, whereas what was actually needed was 300ml. I also believe that the chemicals I was using were exhausted, which further complicated things. Going to do some further tests to make sure this is solved.
(Please note that the slight highlight on the right side is caused by internal reflections in the scanner.)
Experience the horror of the streaking for yourself: