Invalid/blank dates for uploaded files

Have tested the last few versions and still have a problem where uploaded files don't always have a valid date/time when viewed in explorer and some other apps. It doesn't seem to matter what SFTP client I use and it doesn't always happen. Explorer shows a blank date column in detail view and all but 'accessed' is blank in properties. It wouldn't be a big deal but some apps puke when the date/time isn't set and programs that sync based on on date always assume the file needs to be updated. Has anyone else run into this?
Thanks,
Bill