Sorry for the late response…
I’m using Elementor as a page builder.
But even deactivating it won’t resolve the problem.

About the javascript error, here it is:
TypeError: wp.media is undefined[En savoir plus] shortcode-editor.js:333:7
<anonyme>
https://www.wai-zhan.com/wp-content/plugins/fv-wordpress-flowplayer/js/shortcode-editor.js:333:7
dispatch
https://www.wai-zhan.com/wp-admin/load-scripts.php:3:12392
add/r.handle
https://www.wai-zhan.com/wp-admin/load-scripts.php:3:9156

Thanks,
Liwei