@G_G I see:
Upon submission the browser navigates to:
So the URL that it lands on is correct.
If I navigate directly to /form-submission/deleted
I see:
Which is served with a 404
status
It just seems to be your custom 404
page, as it also appears for random other URL’s like:
/this/page/does/not/exist
So I again just fall back to what I said earlier:
Make sure it does.
Make sure the URL’s are correct.
Check what files exist in your deployment with the Deploy File Browser.