Windows Defender Being Disabled

I have a Windows 10 box and just did the anniversary update (it took a long time, which I have read it not atypical). Now, about 3 minutes after boot-up the whole machines stops responding (the mouse moves, but applications will not respond, ctrl-alt-del does not respond, etc.) for about 30 seconds, and finally I get a notification that Windows Defender has been turned off. When I open the Defender dialog and click "turn on", it fails with an error code (I don't have access to the code right now, I will post it later if it is relevant).

I am not running any other real-time scanner, so this should not be a conflict with another such program. My knee-jerk reaction is that I somehow got some malware, etc. and it is shutting off Defender. However, how do I know? Short of throwing a bunch of sticks (scanner programs, etc.) at the problem, is there any way I can troubleshoot and actually *know* why Defender is shutting off?

I am a programmer by trade and like to think I understand some of this, so when things like this happen it is extra frustrating to me. I always think "WFT is going on with this!?" I think I should know how to figure it out, but I don't, and it is embarrassing.

Any help or suggestions would be greatly appreciated.

Thanks,
Matthew

 

Thanks for the reply, sorry for the delay. Of course as soon as I went to reproduce the problem and get the error code, Defender was running normally and no longer shutting down. It has been a few weeks now and it is still working normally. I also did some additional scans with other software and everything appears fine.