Be aware of the behavior the update date of folder displays "Undefined" on OneDrive for Business.
I would like to inform you that the folder occasionally displays "Undefined" instead of the actual updated time by the browser. There is a workaround to avoid this event by updating the browser again.
Since "undefined" is displayed every time I have accessed the folder, that makes me concerned about any influence for another file in the folder. I hope the feature will be implemented to fix this behavior very soon.