I'm disappointed to hear that the recent drivers may not fix this.
i haven't had any time on my gear n the last six weeks for additional trouble shooting, but I hope to pick things up starting next week. I have star party trips planned in August and September, so I hope to get things sorted.
FWIW, I used 5 second delays. For my shorter flat exposures (I had no trouble with longer flats), I actually rotate the wheel between each exposure, that seems to work pretty reliably (that is, I take the flats R-G-B-R-G-B...). For me, these two work-arounds work much better than without them. It sounds like maybe there might be more than one issue going on for you?
Craig