Thanks for reporting this! Sorry for the delayed response. I can reproduce what you describe. I’m pretty sure I know what’s going on. I’ll take a look later this week and get back to you.
The height of the banner is primarily dependent on its content, but you can adjust anything as needed with your own CSS. I’m not sure how well you will be able to fit three columns horizontally on mobile, but you can certainly try with custom CSS as well! Have a look at How to make CSS changes on your site for some tips.