Unable to play a file selected within Synology DS Video

I use VLC for mobile in conjunction to Synology DS Video to play my MKV files stored on my NAS. I browse to the film in DS Video and when I select it I am told DS Video cannot transcode and invites me to play it with VLC. I select this and VLC opens and plays the film. Since I have updated to the latest version of VLC for mobile 3.3.8 on my iPad this no longer works. I get the invite within DS Video but when I select VLC it just opens and fails to play the file. I have to manually browse to it on VLC under Network/ File Servers.

This happened before back in 2019 and the solution then was that the x-callback-url support link had been broken. After it was fixed then it has worked upto installing the latest update for IOS.