With the new board view that was just released, the maximum height of swimlanes/groups in a board is a fixed amount. I use (or: used!) the board view daily to sort feedback to tickets, and now only 5 (or a few more if I select the small card size) are shown at once, and I have to scroll inside that column to see the rest.
I would’ve expected a setting in Board Settings to change this between fixed height and make the box as large as needed for the amount of items in that swimlane.