Hello TacoBot. I am actually working to fix these issues in the new LGM release. Some of them are fixable, some of them are not.
https://github.com/IsmAvatar/LateralGM/issues/227The specific issue you mention, is actually not fixable, it's a known bug in the JDK version you are using. You will either need to install Oracle JDK 8 or downgrade to OpenJDK 7. This is in the GTK look and feel, you can also try under File->Preferences to change the look and feel, but there will likely still be other bugs.
Either way if you switch to the Oracle JDK you won't have any of these problems.