Ok, I will explain to you in simple words-
1. Firstly, I use the FAQ toggle block (with schema) in my post and update the post.
2. Later I decided that I do need FAQ in my post, so I Removed the FAQ toggle block and update the post.
3. now here FAQ is not completely removed by you. once I try to edit the same post again, I can see an empty FAQ box. I removed it again and update the post again. but when you edit the post again, you can see an empty toggle box again.
4. Now, when I run a google search console URL inspection tool, I can see it is showing an error that an empty FAQ schema box exists.
5. So, simply this means, the code of FAQ is not removed completely and permanently after the removal of that FAQ toggle block.
I hope you understand this and fix this for your users. If you are still not able to understand, I am happy to help you with exact screenshots. but here I can not find any attachment option.
I don’t know what it is maybe CSS or JS, or HTML ( not a technical guy).
Once you remove the issue, I will be happy to change my rating to 5 stars.