This may be as it is.
See e.g. this link
https://forums.windowscentral.com/groove-mu...-maddening.html
where other people report the same problem. So I think it is now time to approach the Groove Music team to get it right.
It depends on the features of the player whether you can have multiple artists or not. If that function mandatory for you - then don't use Groove Music in its current version.