IIRC, we already had this conversation.
“AwtPanel extends Canvas” and Canvas is not a “lighweight component” in java terminology (eg: Bug ID: JDK-7012806 Cannot mix lightweight and heavyweight components in an undecorated JFrame )
I don’t have issue with AWTPanel, but @AXELTOPOLINO had issues with AWTPanel ( [Forum] My topic is not available at page 3 only?! - Troubleshooting / General Help - jMonkeyEngine Hub ) Remember, he tried to fork AWTPanel and backport from master some changes.
I created jme3_ext_swing to let it try with a component based on JPanel and not Canvas. And he created a minecraft model editor with it.