It seems that Proton Drive only syncs documents when the last change value changes, not when the file actually changed, which creates a problem. Windows has this annoying quirk where, if the file size didn't change, it won't update the meta data for the time the document was last saved, so even if you saved 10 times in 10 minutes, if the changes you made summed up to the same file size, Explorer will continue to show the change time as being 10 minutes prior, and the updated file with not be automatically synced. To bypass that you should add a "Sync now" button next to "Pause sync," to force a hash check, or add a right click context menu to files force a sync.