I followed the advice in this
thread to convert some webm files containing OPUS format to ogg files.
These now load into MusicBee and are playable, but when I try to edit the metadata I get a validation error.
The files were transcoded using the command:
ffmpeg -i "file.webm" -c:a copy "file.ogg"
I have other ogg files that MusicBee handles ok - but these contain Vorbis format, so I guess the issue is with Opus.