Problem playing MP3

I’ve just installed Mopidy on RPi and configured it to play music to a speaker via the Pi’s inbuilt Bluetooth and alsasink. In the main it works well. I’ve have mounted network shares for both [Files] and [Local] and have no problem seeing the files. However while .wma, .wav, & .mp4 all play without problems .mp3 files refuse to play. Using the musicbox interface (on a PC) I can see the “now playing” progress indicator progressing for a while and then it stops showing “(sync)” on the lhs, when I pause and restart it will progress for a while and then go back to (sync). I can however play the .mp3 files using:

gst-launch-1.0 -v filesrc location=/mnt/DLinkMusic/02-Then.mp3 ! flump3dec ! audioconvert ! audioresample ! autoaudiosink

The Mopidy dependencies show “mad” is missing, but I am under the impression that this is no longer required.
Does anyone have any sugestions as to what the issue might be?
Many thanks