Interesting ... I just turned on the computer, would try it again - but not required - the file in the folder was renamed when I did it above - only those file names were not refreshed on the screen when I've reported the bug. Never seen this before ...
Next time you do a rename on the drive, try opening the folder in Explorer at the same time, then do the rename in Opus. Does Explorer see all the changes without refreshing the folder, or is it similar to what you see in Opus?