Old MSOffice files syncing but status doesn't change

Hi all!

A client of myne has this specific problem, where although old MS Office 97-2003 files get synced correctly, but the SeaDrive client never changes status to finish. It show always the rotating icon and never seems to finish the sync process. Although the file does get synced correctly as stated by the client.

If the file is saved as a new version (docx), the sync process can finish immediatly without problems.

Is there a solution to this (other than opening an resaving all old files)?

Thanks for your help!