MetaSlider with Architekt theme

I have varying caption lengths occupying from 1 to 3 lines. The effect when transition to a different length caption is to force rest of page down or up, which is visually irritating. Is there any way (by CSS?) to set a “container” for the caption to allow 3 lines but retain that height if only 1 or 2 lines are needed? Or just to pad out the caption with spaces or <br> to force this?
Site is using TwentyTwentyOne theme and latest free MetaSlider version 3.20.3

The page I need help with: [log in to see the link]