How to fix bash being 20 lines too big for my monitor?

I’m looking to run Linux on an older Intel NUC. Clear Linux seemed like an obvious choice but I’ve never used it before. I’m not a Linux expert but I know enough to get around and follow tutorials. I’ve installed Clear Linux Server but I quickly discovered that the terminal extends 20 lines below the bottom of my monitor, making a variety of things rather difficult. My monitor is a 27" Dell Ultrasharp, resolution 2560x1440. I’ve tried disabling checkwinsize with shopt, I’ve tried reset, I’ve rebooted a number of times; nothing so far has fixed it. Anyone know what’s happening here?

Thanks in advance.