"collection" pictures are missing or different

When i select “collection” and select “album” or “artist”,
i get an overview from my library with pictures.
Some of them have NO pictures, only icons/dummies for that- doesn’t matter in “album” or “artist”-.
But when i select that album, i do see the correct cover picture,
how can that be solved ?
A similar task is that i get in the overview different picture as the cover pictures,
but that is only for a part not for all albums/artists.
And that pictures also show up when you select a album and play it.
To see the cover picture i have to scroll down the page and select the album again(left click with the mouse),
then the picture appear on top of the screen.
Why is that and how i can switch that off ?
I maybe remember that the sense should that to see newer pictures of the artist as at the date where the record was made.But that is not true for all, on some album even the artists get younger…
Is there a way what i can do or what are they reasons for both issues ?