@gst - how do you specify the URL?
When I put a URL in as below for a song on my Synology NAS nothing plays:
\192.168.1.100\Home\Media\My Music\Andrew Bird\Andrew Bird and the Mysterious Productio\04 Fake Palindromes.mp3
In the logs the URL gets stripped down removing the backslashes from the URL. Not sure if that’s intentional or indicates a problem. I actually tried putting in one extra slash to see if that worked but it did not. 
Could you check your logs and see what your piston is sending in terms of the media URL? This is what my logs show - note that where there were two backslashes (before 192.168.1.100) there is only one backslash instead of two, and where there was one backslash between directory names, there is no backslash:
Appreciate it if you can show what you set for your piston setup to play music. This is how I’m entering it (ignore the extra backslashes in this pic, that was when I tried out adding extra backslashes to see if that helped).
