AddCurrentItemToPlaylist returns error "Currently playing track is not available" from Napster #89

Hi,
I am trying to use the very welcome feature of adding the current track to a playlist. Unfortunately it rejects my action by saying:

{"errorMessage":"Error: Currently playing track is not available!","errorData":null}

(same result when using getMediaList)
I am playing a title from Napster, reading out the current rendererstate yoi canfind in the attached file:
response.txt

Thanks for checking, We are really looking forward to that feature!

Ps.: It took me a while to realize that it starts with a capital "A" despite the usual syntax ;)