I've created a Microsoft Form for Excel with sections and branching logic.
For some reason when I make the form only accessible to individuals within my organisation the form is launched (for users to complete) part way through the form. However, if I change the setting to anyone with the link it launches at the beginning of the form.
I really need to restrict access to people within the org so we can capture email addresses and generate emails on completion.
Have you released form in to the wild or are you testing with a small group? It sounds like a situation we had where people answered first few questions during test but didn't submit. When they reopened the form it picked up from where they had got to. But if you had edited anything in the mean time that could get quite confused. If it is that the solution is to get them to a point where they can submit by entering dummy data and then delete their response. Hope you sort it.