No, there shouldn’t be any difference between front end and back. If I create a text field that is require field and I edit the post/page that the field is shown on front end or admin, I get the same result, a validation error without the page loading or showing the error page that you report.
I did find one other thing that could be causing this, that is any output created by anything other than the proper JSON response to the AJAX query. In other words, something else somewhere is generating output. This problem can be almost impossible to track down. The best way to start is to deactivate all plugins except ACF and change to and unmodified version of one of the 20XX themes and then start adding things until you get the same issue and go from there.
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