If I duplicate a file, I can’t “file, save…” successfully or rename the “filename (copy)” in the titlebar as no file is created and after going through either of these actions the name in the titlebar remains as the copy.
The only solution I have found is to close the window with the original file which will be in the background and then the “save…” menu works.
Saving and renaming a duplicated file is working here in version 5.1 (5B161). What version is your build in the Rhinoceros drop down menu>About Rhinoceros?
If it’s the same, does this only happen with one file or all?