With Build 22478 I see an intermittent problem with file explorer when deleting a system image file.
Right click on the file and delete appears to do nothing and the file is still showing even if it was actually deleted. Gets an error trying to delete again.
The only way to refresh the view in by getting out and back in file explorer, at the point the file is no longer showing.
I have seen this same bug in more than one machine at 22478, but it is intermittent.
I usually see when trying to delete a system image file.