Thanks for all the input! To answer some of your questions:
1) I tried to re-fix, but it made no difference. I'm not sure under-fixing could have been the problem anyway, since those rolls were processed in the same tank.
2) I use a changing bag, not a darkroom. The inner bag has a few holes in it, but the outer bag is intact. The holes have been there for at least 2 years, do not seem to be growing any larger, and have never caused this issue in the past. On the off chance that some films show leaks more easily, Arista Premium 100 & 400 are pretty much my standards which have never had problems, but I've used the same bag with other b/w, color, and slide films.
3) I'm not using bulk film currently as I've had really bad luck with cassettes popping open in the past. (unfortunately, I really need to use bulk film though, I have a lot of it already purchased from before...have been trying to work with re-using regular cassettes but it's not feeding in smoothly even when experimenting with the lights on).
I developed my newest 6 rolls. Two rolls had problems, but not as much throughout the film as in the bottom example from my last post. These are more like the top example, where the problem is much more startling but only appears on a couple frames. The bottom example's problem (previous post) probably occurs on at least 20 frames out of 36 :*(.
1.
2.
3.
Here's how the occurrence of this leak or shutter issue or whatever it is fits into my shooting schedule. I know the dates aren't important, I'm just showing how random the problem seems to be:
April 12 - Arista Premium 400 @ 1600
April 23 - Arista Premium 400 @ 1600 (
damage)
April 24 - 1) Arista Premium 100 (no damage) 2) Arista Premium 400 @ 1600 (
damage) 3) shoot half-roll of Arista Premium 400@1600 (no damage)
April 26 - 1) Arista Premium 100, 4 rolls 2) partial roll Arista Premium 400
April 28 - shoot part of that AP 400 roll
May 3 - shoot remainder of that AP 400 roll
May 7 - 1) morning: Arista Premium 400, 2 rolls (
damage on 1st roll, top example) 2) night: shoot remainder of AP 400 @1600 (no damage) 3) same time at night: AP 400 @ 1600, 2 rolls (
damage on 2nd roll, the bottom 2 examples)
Rolls @400 in D76 from April 26-May 3 + May 7th developed in the same tank. Rolls @1600 in XTOL from April 24 + May 7th developed in the same tank.
Thankfully I do have a nearly-unused extra body that I'd forgotten about thanks to a kind donor, but urgh I have a lot of sentiment for the one that's suddenly causing issues. First my negative scanner craps out on me (these were done on a flatbed), and now this...