Bootstrap nav bar list items clipping issues

Hey I’m finding with many of the bootstrap themes, including the default, there is a clipping issue with many of the standard phone resolutions that causes my list items to clip in an ugly way. Is this a common/known issue? Also is there an easy work around before I start trying to mess with the bootstrap.css files.
All I could find when searching for bootstrap nav bar not working was people forgetting to close li tags, not linking the bootstrap.js, or not giving the body a top margin.

Edit: I am not affiliated with Genesis Zoological, They are a local non-profit that has a very outdated site. I haven’t asked them yet if they want me to rebuild it. I wanted to work on it for a week to have something as an example to show them.