Yes that kinda match the strange data returned by Plex
{"MediaContainer":{"size":0,"allowSync":"1","directPlayDecisionCode":1000,"directPlayDecisionText":"Direct play OK.","generalDecisionCode":2000,"generalDecisionText":"Neither direct play nor conversion is available.","identifier":"com.plexapp.plugins.library","librarySectionID":"9","librarySectionTitle":"Lidarr","librarySectionUUID":"adc9cfd1-bf9f-4081-9a4f-da76ca73d4cd","mediaTagPrefix":"/system/bundle/media/flags/","mediaTagVersion":"1667288622","transcodeDecisionCode":4005,"transcodeDecisionText":"Cannot convert this item. No conversion audio and video encoders could be found in app profile."}}
It says: Direct play OK.
But at the same time says: Neither direct play nor conversion is available.
and size: 0
Does those songs work on the normal plex app? Maybe you moved some data and Symfonium did not detect the change and might require a force sync