Transfering the wrong person using Snom 360 phone

My client has one operator that is in an Asterisk queue for inbound calls. She uses a Snom 360 phone.

Person A is on the line and she is speaking to the person.
Person B is waiting in the queue and is listening to music-on-hold.
Person A tells the operator that he/she wants to be transfered. When the operator transfers person A, she in fact actually transfers the very surprised person B to the extension and is still speaking to a very frustrated person A.

Any ideas why this is happening? I’m using Asterisk version 1.4.6