Blind Transfer isn't working, but warm is

Hello,

We are facing a weird behavior when performing a blind transfer call. If the agent is talking to the customer and then tries to blind transfer a call, it immediatly gets dropped and all communication is ended. In the other hand if the agent puts on hold the customer, call the second agent and then perform the transfer (warm transfer call) everything works fine.

Please let me know if someone already saw something like this or what else should I take a look.

Thanks in advance!