So this is the second time this has happened, shooting bulk-load on my EOS 3, and i think I know why. First time, I was shooting a roll (I think Rollei Retro 100) which I thought had about 36 exposures on (give or take). After 12 or so shots, the camera stops and rewinds. it rewinds with the leader out, so I just reloaded it, set it to 1/8000s with the lenscap on and shot back to the 12th shot, and again it rewinds. I thought at the time that it may have been a 12-shot roll (that i do make sometimes) that I just didn't mark properly as such. When I developed it, I saw that yes, there were 12 shots taken, and 24 blanks. So then my thinking shifted towards it just being too tightly wound and the camera thought it had hit the end of the roll. It just happened again on a roll I developed last weekend. This time a bulk-loaded Tri-X that i didn't roll (bought them from a guy who rolled his own). Same thing, 12 shots and it rewound itself. Same thing, I tried reloading and it got to 12 and rewound. I thought that maybe it was the 'end roll' of the guy from whom I bought it, so just developed it. Same thing, 12 shots and 24 blanks. Looking at this developed roll hanging up, the last frame shot was number 37 on the edge markings. I know that the EOS 3 has an infrared frame counter. I know the 1V doesn't (it has mechanical to protect IR film), but the 5 might have the same infrared counter. So what I'm thinking is that the camera is sensing the end of the roll with a pre-marked spot on the film. Confusingly, it doesn't happen with all bulk-loads, I've shot a whole lot more through the 3 than these two. Could it be that only when an 'end of roll' marker coincides with the 12th, 24th, or 36th frame on the camera-counter, that it presumes that the end of the roll has been reached and rewinds? Has this happened to anyone else with an EOS 3 (maybe 5 or others)? Is there any fix for this that anyone knows of? Is there a custom function / firmware hack (I can't find one)? Blocking the frame counter in the camera is not an option (if it even works at all I still wouldn't, I often use midroll-rewind/reload to swap to other films). Are there any other options besides "keep taking chances" or "don't use bulk-load"?