When using XenDesktop 7.6 on Windows Server 2008R2 with Citrix Receiver 13.0.4, 13.1.4 or 13.2.1 with H.264 Deep Compression Codec, the Windows start menu button flickers.
Problem
Known issue on the server side.
Solution
Enable the legacy graphics mode on the XenDesktop 7.6 server via a policy.