Update progressbar when casting webradio to a Chromecast

Question

I have my own application casting all sort of audio content to CC players, including some webradios (typically mp3 or aac). For such radios, although it's a continuous stream, I have the possibility to get all metadata, including the duration of the current track. As the CC do not support ICY protocol, I've create a tiny custom receiver to which I send metadata update when it arrives. In a nutshell, it does, when receiving a custom message with metadata

    function updateMetadata(metaData){
        try {
          // retrieve current media information
          const mediaInformation = playerManager.getMediaInformation()
          // update its metadata
          mediaInformation.metadata = metaData
          // update current media information
          playerManager.setMediaInformation(mediaInformation)
        } catch(err){
          console.warn("updateMetadata error", err)
        }
      }

That works perfectly fine but I can't find a way to also update the progress bar. I've tried to use BUFFERED and play with media info as well, I've tried to use LIVE and use a container of metadata, nothing works. Anybody with an idea?