Yeah I saw a whole thread about this on a designer forum last week. Someone lost a week's worth of edits on a knitting pattern because Dropbox silently failed to upload the new file. Their client got the old chart with all the mistakes still in it. Makes me nervous to rely on auto-sync for final drafts now. I've started sending a direct email link as a backup every single time.
I mean, I've had zero sync issues with OneDrive across like 50 projects this year. Maybe it's just me but my drafts always update fine on client devices. Idk, could be your local cache or something?