Seems nobody has a permanent fix for this problem since the solution in this topic is only temporary. Guess we have to wait for the next big update in 2017....

Exactly! But I don't have a fix for you yet.
If you wanna get rid of it you'd have to stop the syncing of your documents folder.
You might wanna look here and give it a 'Me Too' ^^ they're offering...

I have this problem on my fresh Windows 10 Pro x64 installtion where the documents folder keep multiplying in the file explorer navigation pane, it sometimes appears when I'm using the file explorer...