Operation can't be completed Finder error code -8076

In Finder I am going to folders and simply highlighting files and moving cursor down so I can count of the number of files in the folder(s). Message "The operation can't be completed An unexpected error occurred (error code -8076).

• Just folders with data files in, nothing special
• Happens with some folders, not all
• (Folders are on Dropbox)
• I can't see a pattern - not always same folder associated with error
• If I force quit & restart Finder then message is gone. Doesn't immediately re-appear, maybe every third time?

Hasn't happened before. Only difference I can think of is I haven't done it with Big Sur before.

Any advice welcome!

Big Sur