This problem plagues me onace a week or so. When Windows 10 is shutting down, Box Drive shutdowns down early before Windows asks to save opened changed docs - so MS Word docs with changes can't be saved if shutdown aborted. I end up having to save locally, reboot, then put the file into Box, then shutdown a second time. Painful, especially at the end of the day.
Proposal - work with Microsoft on a way to delay the Box shutdown point - until after the cancel shutdown message occurs...