With the information given, I'd suspect the problem is with the Citrix ... something akin to a "hanging" session.
It may be that Citrix thinks it still has an open session with the client, so when it tried to re-connect, Citrix says " you already have one session open, so I won't open another" .... but since the client lost original session it looks hung.
If you have a parameter for "max sessions" on the Citrix host, check to see if there's a one-session limitation and open it up (at least for diagnostics).
Also look around for other time-outs or "Allow the OS to conserve energy by putting the into standby or sleep mode."
Some things don't re-associate well when coming out of power-save mode. I have a laptop with a Cisco Aironet NIC (same with others) that, once it's gone into power standby, will not re-associate with the AP.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
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