UI Builder crashed and I can't get it back

I made a minor change to my uss stylesheet and suddenly UI Builder went wild and “crashed.” I have no idea what to do to get it back. In the screenshot, you can see how it used to look in the lower right hand corner, how it looks now in the middle, and the errors I’m getting. I’ve looked but have no idea how to fix these errors and get my project back. Any help would be greatly appreciated. Thank you kindly.

I played the scene and everything went back to its previous state. Very odd and scary.

Try updating the package or uninstalling it and importing it back (UI Builder), if it still does show that error, either the UI file is corrupted or Unity Technologies have got to fix the issue.

Closing the UI Builder window and opening it again fixes these errors., most of the time