User connects to VDI via Native Receiver or from Store front  web URL , they then disconnect (not log off) and can no longer reconnect to it until that disconnected session is logged off, or the ICA service is restarted (which logs user off).

ERROR in Event Logs:

Event ID 1, ICA Client (Vanadium) The description for Event ID 1 from source ICA Client (Vanadium) cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer. If the event originated on another computer, the display information had to be saved with the event. The following information was included with the event: Vanadium: TW Protocol error: Execution failed (Code -1) Cmd = CMD_TW2_TEXT_TRACKING_DRAW The data containing the error is below (1033 bytes)
 

Solution 1: Enable legacy graphic mode policy; New graphics has more applications and services, which can get blocked by 3rd party services like AV and  that is the reason why legacy graphic policy helps as it would not use the new graphics. 

Solution 2: Upgrade to VDA 7.6 FP3.
It’s a combination of few things here like receiver version, set of policies and version of the VDA as all are related in graphic scenarios. We have seen intermittent graphic compatibility issues when we have different versions of above mentioned component. Few such issues have been addressed in the LTSR release 7.6.3.00.