DAVdroid connects to the server and tries to connect to /my-hidden-dir/remote.php/dav .
As an answer it gets a 401 Unauthorized answer with a Basic auth request.
Why does it get a 401? It sends the Autorization header preemptively. Maybe the IP has been locked because of too many attempts? Is there any info in the OwnCloud logs?
I would expect either that DAVdroid tries to connect with correct Authorization headers starting with the first attempts
That is how it behaves here, and how it should behave. Are you sure that there is no problem with the password? Does it contain non-ASCII characters?
Can you provide the necessary steps so that we can reproduce the problem? Without that, I can’t do anything.