Frequently see Java.lang.Exception errors in the UNC error log or Standard output window that reads, in part,
"At tridiumx.gcm.GcmUnsolicitedReceive.run (bytecode xxx)"
TAC I/A Series
I/A Series R2 UNC
I/A Series GCM 84xxx or GCM 86xxx connected to UNC
The GCM does send unsolicited messages all the time, more or less depending on how you have the logging configured in the GCM. Depending on the source of the message, some will simply be reported to the Standard Output Window as "Unsolicited GCM message received" or "Processing Unsolicited Message"'. Other messages will be reported as a part of an error message written to the Standard Output Window and / or the Error log.
You can minimize these messages by insuring that none of the print groups in the GCM are configured to use the serial port to which the UNC is connected. You also need to confirm that all of the Exception Print Flags in the GCM are set to NO. The remaining messages that cannot be eliminated are almost always GCM Network communications protocol messages that have no meaning to the UNC.