In building one of my latest environments on Server 2012 R2 with XenApp 7.6 I noticed a strange phenomenon, when logging in, after the processing of my Group Policies my XenApp session would hang at a black screen for about 10 seconds as seen in the screenshot below:

XenApp 7.6
XenApp 7.6

After wrecking my head disabling GPOs, using Citrix and MSFT Folder Redirection, disabling asynchronous logons and the whole roundabout of troubleshooting steps, it seemed that nothing was working.

I then proceeded to do a trace on the issue and noticed that my logon was being hung by wfshell.exe which is tied to the Citrix session process. It turns out that there is a private hotfix for this issue which is tied to Server 2012 R2 running XenApp sessions. The hotfix is CTX142036.