I would need to take a closer look at your site. So I would need to request temporary access (WP-Admin and FTP) preferably to a test site where the problem has been replicated if possible in order to be of better help and check if some configurations might need to be changed
Your following answer will be private, which means only you and I have access to it.
✙ I would need your permission to de-activate and re-activate Plugins and the Theme and to change configurations on the site if required. This is also a reason the backup is critical.