Symantec Endpoint Protection Error analyzer/processor submits data to Broadcom Symantec for analysis regarding process crashes. Symerr.exe process is conducting a ipconfig /flushdns to help remedy network connection issue as part of a self heal feature of SymQual. This feature tries to rectify any network related errors. One of the steps is to release the IP address via iphlpapi calls. This release and renew of the IP address results in the Citrix connection drop.
This issue is fixed with the release of Symantec Endpoint Protection 14.3 RU4
To obtain the latest release of Endpoint Protection please see the document Download Symantec Software, tools, and patches