Assuming nothing is working on the archive in parallel, my guess is this is caused by your antivirus scanning the destination archive and holding it open while Opus is trying to replace it. If so, clicking Retry should work once the virus checker releases the file.
The scan may be triggered by the Replace File dialog in Opus generating a thumbnail of the archive based on its contents (causing the archive to be opened, which may then cause it to be virus-scanned).
Good virus checkers only scan files once until they are changed (or there is a virus definitions update), but some of them scan files every time they are opened. Microsoft's antivirus is particularly bad (in almost every aspect, these days, sadly).
If you don't have any control over the antivirus, you could try preventing the thumbnail from being generated on the Opus side. (Preferences / File Display Modes / Thumbnails, Adjust folder thumbnail settings, then turn off Generate folder thumbnails from images inside folders.)
Another thing which can passively cause archives to be opened is the folder tree, if it is open. Try turning off Zip files and other archives under Preferences / Folder Tree / Contents.
It's also possible it is not antivirus but that there is something about the particular archive (and maybe others made by the same thing) which is causing things to get stuck. But antivirus would be my bet here.