Thank you for contacting us and I'd be happy to assist.
Due to the nature of this error and IP restriction, it will be more efficient, if you could share a clone/snapshot of the website, where this error can be seen. This will allow us to troubleshoot this on a test server and will reduce the time in back-and-forth communication.
( ref: https://toolset.com/faq/provide-supporters-copy-site/ )
Note: If it is a large website, you can exclude the media (uploads) folder from the package, to reduce the size.
As for the other ticket, the information provided by Luo is correct and let me explain this, from a different angle:
1. It is a WordPress thing that if you'll try to create a page/post with the same name/title, it will be created, but to keep the slugs unique, it will append numbers ( -1, -2, -3, ..... ) at the end of the subsequent slugs.
You can confirm this behavior, by creating 3 posts or pages, with the same name "Test" on a test website, without any plugins.
2. Your assumption that Toolset Form without the title field will generate a unique title each time, is not correct. The automatic title is generated using the IP address of the user submitting the form, so if the same IP address is used again to submit the form, the generated title would be exactly the same too. However, as explained in point 1, the expected/default behavior is that the slugs of the generated posts will have incremental numbers appended at the end.
Again, you can confirm this behavior by using a Toolset Form on a test website, without using any other third-party plugin or custom code.
3. If on your website, yours and Luo's test confirm that only when the "Permalink Manager Lite" plugin is active, generated posts are saving the same slugs for multiple posts, then that means that this plugin is interfering with the WordPress default behavior of maintaining the unique slugs (point 1) and you can consult its official support and documentation, to see if it can be made to respect the unique slugs rule.
4. In case, the "Permalink Manager Lite" plugin doesn't have any option to respect the WordPress default behavior of maintaining the unique slugs and you absolutely need to keep that plugin, then you should end your reliance on the Toolset's automatically generated post titles and slugs. On the form's submission, you can use the "cred_save_data" hook ( ref: https://toolset.com/documentation/programmer-reference/cred-api/#cred_save_data ) to set a custom and unique post title and slugs, which can be a combination of, for example, user's ID + Post ID + current time stamp, etc.
You'll find an example of a code snippet to set a custom post title and slug on form submission, in this support thread:
I hope this helps and I'm setting your next reply as private.