Hey,
I encountered the same issues on 15 of my rigs actually. We are using windows 10, windows defender disabled. I will rollback tonight to 4.5 since 4.6 has been very unstable for us.
It's actually the first time that I see all my rigs with yellow/red warning on ethpool with 20-30% rejeted shares. Also, we had ethdcr.exe that has stopped working as a common thing (the windows error thing that is stopping that application). It seems to happen all at the same time as well, on rotation. Hopefully we have some UBNT mpower to restart our rigs when the power goes under 500W.
We had that problem that was happening once in a while, but nothing like that since I updated to 4.6.
Anyways, keep the good work, we are just going back to 4.5
My test rigs are mining on ethpool currently, for 60 hours without restarts, five rigs, no rejects. PM me the log so I can check rejects.