Given two users using a kanban with realtime and given user Alice had never opened (and therefore never loaded) column 'Review'
when user Bob moves a card from 'Review' to any other column
then Alice will see the card appear in the new column BUT the card count at the top of 'Review' will be wrong (not decremented).
Technical information
This only happens in this direction: if you move a card from an open column to a closed one, it will work.
This happens because on Alice's side, the card has never been loaded, so we do a GET request to retrieve it, but its "in_column" attribute will already be the new column. That means that the kanban cannot know where the card comes from and cannot update the source column.