Unexpected Voice Prompt TRANSFERRED during conversation call


We using Elastix 5.2.x version installed in HP LM110 server, PSTN Line, Alcatel Analog Phone and ATA Voip Adapter, the system is running over a month but the only problem we’ve encountered is interruption of voice prompt "Transffered " during our agent conversation to customer. We using hook flash to transfer call instead of feature code. Can anyone help me how to solve this issue.