Master slides Randomly Changing

This may not be a solution, but I did find that one slide spontaneously changed to a different Master while I was working on the .story file. I tried to apply the previous layout, but it was no longer available as a selection. Only the default masters were selectable. So I closed the file and waited. After my OneDrive completed the upload that was auto-saved, thus synchronizing the file on my hard drive with the OneDrive, I reopened the file, and the slide was restored to the original Master layout. This suggests to me that it is futile to change slide layouts when this happens. Something else is going on. Perhaps file saving permissions are being violated during the automatic upload process.