Windows 7 SP1 x64, Office 2010 SP1, Windows 2012 R2 share; sometimes, when a user opens an office file that is in use by another user, the splash screen displays "downloading... (0%)" for 30 seconds before the "file in use" Windows appears. When this happend for the first opening, the next ones are quick as usual for the same file.

Hi,

Please try to add the Windows 2012 share path to the Trusted Locations in the Trust Center, then verify result.

Also, you might want to use Network Monitor to track what specific process is runing during the downloading period.

A.B