windows defender update fails after 16299.309 update

my system has updated to 16299.309 ok but i keep getting a failed Windows Defender update error
it's says it's downloading, then installing, gets to 100% and then throws error message below:

"Definition Update for Windows Defender Antivirus - KB2267602 (Definition 1.263.659.0) - Error 0x80070643"

i tried many fixes including the Trouble Shooter, SFC, resetting download history (batch file from Brink) & ended up reinstalling windows 10 (keeping programs, files & settings) but no fix.
if i try to update directly from defender i get "error code - 2147023293 ...Fatal error during installation"

Disk Cleanup of system files is also problematic & doesn't complete on its own.. has to be stopped & restarted numerous times but ultimately seems to delete the required files..

since i reinstalled windows 10.. do you think it's a setting that was retained from previous install that is stopping it from working? i've wasted hours on this and i've hit the wall.

well the problem has fixed itself..
tried manual updates again today and all went fine.. no errors..
hope it stays that way..

...and it's back