This is a known bug in List View or Shelf View, depending what view mode you had on when it got first introduced.

EDIT: To add that it still works as should in the unaffected view mode. For example, I'm affected in List View, but it works fine in Shelf View for me.

I've contacted GOG Support about it, they said they knew of it but it was not high in their To Do list at the time.

I assume it will be addressed when these pages get the revamp.