The F100’s broken door latch is a known weak point, and used replacement backs may fail the same way. A more durable fix is to reinforce or replace the broken plastic latch with metal rather than simply swapping in another used door.

Reported repairs include attaching a shaped metal piece to the inside of the film door and bending it to recreate the latch. This can be screwed or otherwise fixed in place and is likely to outlast the original plastic. Community reports also mention independent technicians making custom metal latch repairs for F100 doors.

If you want to DIY, the good news is that the F100 film door is easy to remove: the hinge uses a spring-loaded pin, so you can detach the door for bench work or to send it out for repair.

Another practical option is to buy a complete donor F100 rather than only a replacement door, since doors with intact latches are often harder to find. However, this is still only a parts swap, not a permanent redesign.

So the best long-term route is a custom metal latch repair, either DIY if you’re handy, or through a camera technician who can fabricate the part.