please check whether the assignments are completed and closed. Default Submit button automatically does that. if your have inserted a custom button , Give finish assignment action on click of that button.
Mahipal is correct. There are no custom scripts or any code modified. If you check in the product application itself (7.1.9), this issue exists. You may say this is default behavior, but it's incorrect and should be fixed by Pega. The fix below provided by Pega doesn't solve the problem.