Please verify that your UE is either setup to auto answer the call or that the UE file is set up properly:
If using AT command interface for accepting incoming voice calls:
UE interface -> control method = AT
UE AT Interface -> commands -> Ensure Idle = "AT", Accept incoming call = "ATA"
Important: If you leave the control method to 'manual', Test Manager will assume that the CS voice call is established. As a result, the UE will remain in CC mode 'ALERTING' and release the call after several minutes. This will appear as if the CS call was dropped.