My LS420D started acting up the last two weeks where it would allow Active Directory users and groups access a shared folder for a while and then quit. The NAS was accessible via web page, but would not show the Active Directory users and groups. A reboot got it all working again for a short while and then it would quit sharing again. I realized the only thing I had updated recently was a security update from the Active Directory, Windows 2012 Server on November 18th. After numerous tries at resetting the Active Directory on the NAS with it working for a while and then failing after minutes or an hour or so, I decided to roll back the Windows Server 2012 updates to see if that solved the problem. Turns out, after uninstalling KB4467701, the NAS is working flawlessly again for several days. I don't know what is in the Microsoft security update, but it broke my Active Directory NAS access, so I have removed it for the time being. Would be nice if Buffalo could track down what about that update is causing problems.
