Why is JMenuBar and UIManager bugged?

Question

Java

Guys, in general, I had a problem with the fact that when changing the UIManager, JMenuBar is bugged. Here are all the screenshots:
Before changing the theme:

After:

That is, when, after changing the theme, I again click on one of the buttons ("File", "Editing", "About"), something appears that looks like a gray square under the "Edit" button.

Change themes with this command:

UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");