"Citrix Sign-On Failed" error on 5470 randomly

Hello, 

We have around 200 thin clients that can run ThinOS 8.6_807. We are experiencing an issue with a random Citrix Sign On Failed error, a user will login and get the error then 15 minutes later they will login again and go right through. Was wondering if anyone else has seen anything like this, and any recommendations would be helpful. 

Thank you!