I'm digging around in the dark here, out of horror and sympathy for your angst. With the break occuring on top on horizonital stems, I've got to wonder if it's a stem weight thing, where the stem is understrengthed or too brittle to support the weight of the bud.
Don't really know, and will wait to hear the pros chime in.
If you want to try a stop gap on the remaining buds until you know more, set a stake right at the bud's neck and secure the stem there. That will take the weight and the strain off the stem before it breaks all the way through.
Best of luck!