Pre-fill Responses in Your Microsoft Forms

Having multiple unique pre-filled form URLs for the same user to the same form now seems to be working correctly.  I have the same experience now as JAS108 shared, including receiving the pop-up message if a previous attempt to fill out the form was unsubmitted.  If all previous attempts to fill out the form for that user have been submitted properly, or there are no previous attempts to fill out the form by that user, then the pop-up does not appear when the form is launched again. The values pre-filled in the form match the values provided in the pre-filled form URL every time.

I also wanted to share that because the pre-filled form URL issue appears to be resolved by Microsoft, you can easily use Power Automate to create the custom pre-filled form URL, using variables or values from other data sources (such as SharePoint, Excel, etc.).  

In this example, we have a support request feedback form that is sent to the requester whenever a support request they submitted has entered a closed status. In the Power Automate screenshot above, I shortened the MS Form field ID in the pre-filled form URL to allow for a good screenshot, so it appears shorter in length than what is actually there.  Below is the pre-filled form URL used in the action.  

https://forms.office.com/Pages/ResponsePage.aspx?id=YourMSFormFieldID=@{triggerBody()?['NameOfSharePointListField']}

In the SharePoint list, we have fields to contain the requester feedback form data.  Feedback responses are input into the feedback fields in an existing list item, by matching the Support Request ID supplied in the MS Form to the SP list item ID. This is done through Power Automate.