Cannot publish/create FAQ article – “Response is not a valid JSON response”

Hi, I cannot publish/create new FAQ articles anymore (previously I was able to, around two months ago). I get the following error message shown in a red banner at the top of the editor:

“Updating failed. The response is not a valid JSON response.”

I am using the default block editor. My website is running WP 6.5.2, PHP 8.2. There are no related error messages that show up on my debug.log file. I have updated all my plugins. What could be causing this issue?

Pulling my hair out right now. TIA!