There may be instances where you have the following in your directories, which are found in folders synced by the Dropbox client:
A file named
.dropbox
A folder named
.dropbox-cache
These two are disallowed on Dropbox by default, as explained on these guides:
https://help.dropbox.com/installs-integrations/sync-uploads/files-not-syncing
https://help.dropbox.com/files-folders/sort-preview/file-name
An error message will pop up if you try to sync these files and folders:
