I don't know 
Leave this option open and students or teacher will find a way to get this error.
But... I also found this error with a very old Questionnaire, I think from 2015 or something. During all the upgrades I think the questions were simply not connected to the rose-feedback anymore. It was in an old course, not used for years, where I am pretty sure it used to work OK. But when I recently tried to open the Questionnaire, this error came.
Leave this option open and students or teacher will find a way to get this error.
But... I also found this error with a very old Questionnaire, I think from 2015 or something. During all the upgrades I think the questions were simply not connected to the rose-feedback anymore. It was in an old course, not used for years, where I am pretty sure it used to work OK. But when I recently tried to open the Questionnaire, this error came.