I'm currently in the process of updating SolidWorks, along with Workgroup PDM, from 2014 to 2016. Is there any known issues with skipping an entire version? I would assume that all 2014 files would be backwards compatible with 2016 and could be updated by either using the Task Scheduler to do this or by opening, saving, and checking the documents back into the vault as needed.
Check your server. We had to update our server when we switched from 2014 to 2015.
http://www.solidworks.com/sw/support/PDMSystemRequirements.html