Thank you! I wondered if that was it, but wasn't sure. I've spent the past 20 minutes messing with the volume of o2 my generator's putting out (I don't actually have a way to control pressure since it's not a tank), and that's helping.
I also think I was making a mistake by leaving my o2 torch valve closed while I was running the generator but not using the torch. Maybe I was creating a buildup of o2 pressure that was blowing out all at once when I introduced it to the propane. Why this is only a problem now instead of past months, who knows, but there it is.
Now I'm leaving the o2 valve on my torch open while the generator's running (though not when I'm lighting it, clearly). That plus lowering the volume of o2 from the generator = two successful bezels soldered so far.
Thanks again. Very helpful!