Error on submit: The form submission was unsuccessful. Please try to submit the form again

On NAC forms we sometimes have users report getting an error on submit: ‘The form submission was unsuccessful. Please try to submit the form again.’ Typically trying again doesn’t resolve the issue, the same error simply displays again.

Does anyone know what the rules are around when/why this error displays? I suspect it’s a timeout issue: where a user keeps an authenticated form open without a submit for too long. I could be wrong however. If someone does know however I suspect the solution is to add a ‘Save’ button to a form and have users regularly save.