I too would like to know. I have fought this for over a month. I am not even sure it is me, or just something with WU's I am getting, but I get a lot of rejected ones, after it churns through it for hours.
I have changed nothing on my end, nor have I slowed folding. I have tried 10-15 different versions of drivers also. The machine that is on Win 10 beta fast ring is fine, the other is the one that is having issues.
This all started the 27th of Jan, when things started to drop off. I feel it is something to do with Win 10, as I have noticed it appears that you Roland have been fine this whole time.