This is something that happened starting a few weeks ago. We upgraded to the latest firmware 2.82 on April 6th and since roughly around that time, the client has been noticing that every so often the lock files (the hidden files that start with ~ when opening a document) that Word/Excel use don't work properly. Sometimes even if the lock file exists, Word/Excel will not warn you that the file is already open and to open as Read Only and allow you to save over a document. We've been using this NAS since last November and this only recently became a problem. It's difficult to replicate as most of the time the locks work and it gives you the prompt.
The reason I'm thinking this is a NAS issue is because they had an old Windows 2003 server they were using for 8+ years and never had any problems like this - and have had the TS since November and it was never an issue and it seems to correspond with the latest update, most likely.
I can't find anything related to a recent Office 2010 update and lock files not working properly and it's organization-wide about 25 users.
Has anyone else seen this type of issue since the update?