Sorry to hear about your experience.
I am not sure what is causing the problem…but have you contacted Hotline (edhoy.com) and asked them? The only time I have had this happen to me was when I used a basic kiln wash that came with my kiln and fired opaque glass. Not that is keeps it from happening again, but you can soak your pieces in vinegar to remove the kiln wash and salvage what you can.
I use Primo kiln wash and noticed that they have changed it. My experience with the new product is that is lasts longer on my shelves, especially when I do Paul’s kiln pressing. Before I would only get one firing per coating, now I have gotten at least 3 firings before I have to re-apply.
I do apply my kiln wash by spraying.
I just read the directions on the new container and it does mention “Mixed solution will precipitate to bottom of container. Shake vigorously.” ….must be why they have now include the marbles in the pkg, -to make sure it gets mixed well. Did you stir the kiln wash well while using it?
I know a lot of people use a garden sprayer to apply kiln wash…I have had very good results using the 99¢ spray bottles from Target. One of the sprayers last quite awhile. I mix up the kiln wash in a jar with the marbles and when it is stirred well I transfer the mix to my spray bottle, including the marbles. I shake/stir the sprayer very well before and during application.
Hope this helps,