The problem I'm running into is that I initially built this and several other similar circuits with the first bunch of diodes I had to hand without particularly looking at them. It turns out I was using some germanium diodes from an old radio project. They are 1N276 and something in a glass case with a green stripe but no part number. I only had a few so I couldn't continue with this project until I got more diodes. I tried 1N4001 and 1N4003 because I had them on hand, but didn't expect them to work (they didn't). I then bought some 1N4148's which I did expect to work since they are "small signal switching diodes". Unfortunately, the resulting outputs just oscillate wildly.
I'm kind of baffled because the diodes I would expect to work perfectly for this application don't, and the diodes I would never have specified for this circuit work perfectly. Any ideas as to why this is the case and a proper replacement part that will work as expected?