[pkscout]

Start with first song - display of artist and accordingly fetching audiodb and fanart information works correct
Next song (2nd song) played automatically - no information about artist (cover however is displayed)
switch back manually to first song and then manually to second song - all information are displayed correctly.

It looks like you're using the Google Music plugin most of the time, so I installed it to see what I could see. It seems like sometimes the plugin provides all the information you would expect so that the music looks like a locally playing file (i.e. there is a title, artist, album, year, etc in the music visualization). Then other times it doesn't do that and all I get is a single line with artist - title. When I get the latter, if I go back to the previous song and then go forward again I get all the detail. So it seems like this might be an issue with that plugin. When it properly populates information for Kodi, AS gets images as I would expect, when it doesn't, AS thinks no artist name was provided.

Other issue again regarding "Mumford & Son". Name indicated by google stream ist correct however artist name is only "Mumford" which will result in not getting information from audiodb and fanart. No sure whether this has something to do with your script. Do you have an idea why only a part of the artist name is fetched?

Since I have a free Google Music account I don't have any way to test with a particular artist (at least not that I've figured out). I did test with a local file, and Mumford & Sons worked fine. So I'm leaning towards an issue with the Google Music addon and artists who have an ampersand in their name. I did find an error with theaudiodb search with artists with ampersands, but that isn't the problem you're having.

I think at this point it might be worth you asking a few questions in the Google Music addon thread.