Session Reliability is configured and enabled and when user connections are going through a NetScaler 10.x Device their sessions are dropping or disconnecting.

By-passing the NetScaler 10.x device allows user sessions to not disconnect or drop.
Disabling the Session Reliability feature also allows sessions not to disconnect or drop through the NetScaler 10.x device.

If you examine the event logs of the XenDesktop Virtual Delivery Agent (VDA) when the issue occurs you will see the following events:

Event ID: 1006 
Message: The session has been interrupted.

Event ID: 1007
Message: The session has been resumed.

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If using Session Reliability ensure you do not have any of the ICA Keep Alive Citrix Computer Policies enabled as the features do not work together, then set the following registry keys on all XenDesktop Virtual Delivery Agents (VDAs):

[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\XTEConfig]
Name: CgpClientToServerKeepAlive
Type: REG_DWORD
Data: 0

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\XTEConfig]
Name: CgpClientToServerKeepAlive
Type: REG_DWORD
Data: 0

Note: If the XTEConfig registry key does not exist you must create it. What this registry setting does is tell the server to not look for a ICA keep alive packet from the client in order to keep the session active.
ICA Keep Alive packets are small network packets sent at pre defined intervals (Configured through Citrix Policies) to the server to keep an ICA session from being disconnected and are not needed when using Session reliability.

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Problem Cause

The problem is the Citrix VDA is not receiving an ICA keep alive packet from the client when the connection is going through a NetScaler 10.x device which is resulting in a session drop or disconnect.

In XenDesktop 7.x with Session reliability enabled users sessions are being dropped when the connections are going through a Netscaler 10.x device.

This is an alternative feature that can be used instead of Session Reliability they just cannot be used together. Refer to the following links:

Citrix Documentation - Configure Session Reliability

Citrix Documentation - ICA Keep alive policy settings