WPDiscuz Frontend Moderation and Defender Pro
What do you mean by that?
To find the reason of the issue the developers will need to modify the wpDiscuz Frontend Moderation add-on files. Please read this article to learn more about plugin editing feature: https://www.webhuntinfotech.com/enable-theme-plugin-editor-wordpress/
I talked with the developer and they did thorough testing of any compatibility issues. They say the problem is caused by the frontend moderation plugin.
So I would ask you to have another closer look at the problem, maybe you can find the issue.