If you open Office 2003 files (.doc, .xls) files with Office 2016 on a Vault you'll get a locking error message from Office. Newer Office files (.docx, .xlsx) don't show this problem.
The error is caused due to the filesystem that the local copy of the Vault has. With the Nomadesk 6.0.8 (live on October 6th) update this problem is resolved by removing and re-importing your Vault locally, which will make a new image file with an updated filesystem.
If you have any additional questions, please contact our support team.