Dropbox files giving warning message

A new frustration, started recently. When I move or copy any Dropbox file, of any type, to another folder - even another Dropbox folder - I now get the daft message shown below.

These are local files, made by me, owned by me. Only happens when the start folder is in Dropbox. I can move or copy files outside Dropbox into a Dropbox folder (or any other folder) as usual, with no silly message.

I've also posted to the Dropbox forum but from experience I'm not optimistic.

Terry

If the files are being blocked see this tutorial:
Unblock File in Windows 10

IMO Windows is right to block dropbox files, it should mark it as PUP all together.

Thanks, I'll study that video shortly. Meanwhile I tried a few files in the Dropbox folders whose file display the warning, I'm unsure where in Properties I would find whether it was blocked?

Right click file, properties, under "General" tab in bottom right corner there should be "Unblock" checkbox.

Thanks, appreciate the fast response.

The dozen or so files I tried at random within the culprit parent folder had no Unblock in Properties. It has 25 subfolders and several hundred files. Manipulating any of them prompts the message. So can I conclude confidently that none are blocked? IOW the cause lies elsewhere?

Press windows key and type inetcpl.cpl and hit enter

According to message in your initial screenshot this is where you should be able to unblock all files at once.
But I don't know which option may do.

Other threads earlier took me to that Internet Options window, then into Security > Local Intranet > Sites > Advanced, but I'm out of my depth with that stuff.

I've narrowed the issue down to a single large folder: C:\Users\terry\Dropbox\3D Printer\
(I have some 320 DB folders and use maybe a score frequently. But not yet encountered the msg in any of them apart from that one.)
Here's a screenshot that pretty well sums up where I am:

dropbox.com/s/jty105l1exdpepi/AddedExtension.jpg?raw=1

I've probably read 50 or so threads over the last two days and revisited many Win 10 settings. Also Internet Options, after seeing advice that the cause may be down to Intranet settings. But this is a solo use PC with no 'intranet' AFAIK!

EDIT: I eventually did find a file (a downloaded ZIP) that had the Unblock option and I did so. (The Unblock option then disappears.) But still got the message when I tried to manipulate the ZIP. I'll try a PC restart later but not optimistic.

Not intranet, look for internet instead.

If you don't see it or there are no options, click on "reset all zones to default.." and it "internet" should appear.
Then choose "custom level" and there you'll find file specific settings.

Or you can set level to medium or lower.

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btw. if you have problem with those zones see:
IE Security Zones - Enable or Disable Level Settings | Windows 8 Help Forums