I have a card with connectors between items within that card. If I collapse that big card (it is there for reference) the connectors remain at the position relative to the "title bar". They move with the card. I do not see how this can be a feature, so it has to be a bug ;-)
Indeed, it is a bug. Collapsed cards is something that has not got a lot of love yet. It is on our list, although not very high up yet (vote here everyone, if it gets on your nerves! ;)
In the meantime, what might help is to switch "Show Connections" off (see screenshot, or just press ctrl+L) then, at least these irritating ghost arrows leading into the void are only shown when the linked card is hovered on. (Unfortunately this setting is not permanent but it will be - probably earlier than the bug fix).