when you inciating a blind transfer, the spa first put a hold (send an INVITE with sendonly), then ask for digitis and then sends the REFER. If the REFER is answered 202 Accepted it just closes everything (OK), but if the answer is 488 it does nothing, it would be better to pickup the call again without user intervention.
I have tried sending INVITE with sendrecv without success (replies 200 OK with sendonly).
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