MpCmdRun runs permanently with massive log files

Fragmentation check shows I have huge log files (and log.bak) at
C:\Windows\ServiceProfiles\LocalService\AppData\Local\Temp

They show a log entry at least twice per second EVERY second as follows
----------------------------------------------------------------------------------
MpCmdRun: Command Line: "C:\Program Files\Windows Defender\mpcmdrun.exe" -wdenable
Start Time: ‎Thu ‎Jan ‎21 ‎2016 10:00:59

WDEnable
ERROR: WDEnable(TRUE) failed (8007139F)
MpCmdRun: End Time: ‎Thu ‎Jan ‎21 ‎2016 10:00:59
-------------------------------------------------------------------------------------


What is what trying to do, and why doesn't it learn and stop?
How can I get rid of the problem?
Thanks

[ windows 10 Pro 1511 10586.63 ]

Thanks Z - that's a good comprehensive link.
I'd already got as far as AV being a likely cause.
Having changed the way my AV is set up, I now have mPcmdrun log which tries at startup for about 4 minutes and then goes quiet.
I'm happy enough with that.
Anyone finding this thread should check Z's link above.
Salve!

This is getting ridiculous. I thought it was solved, in that it only ran briefly then stopped.
However, it pleases itself by the day, and most of the time it just runs, and runs and runs......
It's thick - why does it run at all, and why doesn't it stop?
Meanwhile, most of the disk output on my machine is this stupid program generating Huge, pointless error logs.
[Ztruker, thanks for your last - via 3 (separate) AVs, for interest. And no - why would I be forced to run as a defender a suite of programs which was this incompetent. If it's too stupid to get it's own settings right, why would anybody expect it to defend against competent programmers? ]