During the deployment of a new Citrix XenApp 7 environment (Windows Server 2012 R2 for both VDA and StoreFront), there has been a strange issue that was nearly impossible to replicate. Sometimes users would call and say their applications were flashing back and forth with a black screen. Upon remoting into their machine I can see that is the case. The only fix I found to get them working again was to log them out and back in, which worked 100% of the time at the cost of them losing any unsaved work. Here is a video of the issue to which I am referring:
After researching various fixes and causes it seems to be something to do with monitor resolution and/or changing the DPI (Make text larger or smaller in Display Settings) on Windows 7 specifically. I am unable to replicate the issue on my Windows 10 desktop, but on Windows 7 here was the process that seemed to cause the issue consistently. Log in at one DPI setting. Launch XA and a couple of published applications. On the desktop machine change the DPI setting and log out without logging your self out of your XA session. Log back into the machine and launch a published application. This should reconnect your session, and the black screen flashing should begin. I tried going back to my Windows 10 machine with a flashing black session and reconnecting, but the flashing continued.
EDIT: I posted this over at the Citrix XA 7 Forums (https://discussions.citrix.com/topic/391607-applications-flashing-between-monitors/?page=0#comment-1991810) and it does not seem to be getting any traction. Ugh!