This is interesting - I have kind of similar experiences, over long time.
Some times, but without notices or other specific situations to connect directly to the crashes; open excel files AND directory opus freezes when trying to open other excel files from the directory window.
I can not assure that this also have happened when I don’t have the previewer window open - but I will observe this from now on.
It seems that this is more likely to happen when I have a number of excel files open - - more likely the more files open (6-8-10 files, individually not very big or complex).
Since this seems not to be only my specific configuration/windows related , it is interesting to know more about what causes the problem.
I have QuickView installed as file viewer, but it seems that also the “microsoft excel previewer” often is active (and reports an error: This file can not be previewed because of an error in the Excel Previewer" )
When killing the two dopus processes with task manager, the frozen excel file windows normally returns back to “live” status, and I can save the files normally. It is not enough (or even possible) to just close dopus by normal “file exit”.