Search does not find Artist

I have installed Volume on a Raspberry PI3 using HifiBerryDac+ Pro.
Everything is installed and works fine despite of the search function not finding some of my files.

E.g. when I search for Metallica I get a result back from Lou Reed together with with Metallica, but not
the Artist itself, same for a Group called “Live” . Searching finds all albums where Live is in the name, but not the artist.

I checked the ID3 Tags (not only in iTunes , also using another tool) and they look ok to me.
What version of ID3 do I need so that search works 100% ?

Thanks in advance for any help and/or hint.