I guess the error is related to DropLocation mentioned in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MpSigStub. Some kind problem was there with accessing that folder (or files in that folder). That's why deleting that folder may have worked. Generally, this folder is created while updating and deleted afterwards, created again when updating again and then deleted. But, maybe something prevented it from getting deleted (Tuesday updates?). Phew! Tough task to guess. But good news is that clearing Temp is working. :-)
If error happens again, try clearing Temp once more. Observe it for some days. If error occurs repeatedly then upload MpCmdRun.log and MpSigStub.log on OneDrive and post links here.
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