The difference column may indicate a high difference between recording and replaying. It does not mean that the replaying is not working. You should use the compare response feature to see if the response is of the same type or not.

The big differences might be due to dynamic values that are different especially if your input data are not the same. In other words you may be overlooking something that should not.

If your user is creating something in your application or/and database, you should directly check in your application if you see something related to the user validation. It's the best way to make sure that the script is really working.

You can also add some validations on some server responses to validate their content.

See the NeoLoad documentation here