Using SCA on a UCM6202 - phone is a GXP2170. SCA works just fine, account(s) and VMPK(s) set up properly, etc.
However, if I answer a call coming in on an SCA line, I am unable to transfer the call. Neither a transfer VMPK nor a manual transfer works - the call just immediately comes back to me as soon as I press transfer.
The REFER request is receiving a response code 400, state 5. To be clearer, the REFER gets a 202 accepted from the UCM which is then immediately followed by a sipfrag NOTIFY 100 trying and then a sipfrag NOTIFY 400 Bad request.
Any ideas? Transfer works properly on non-SCA lines on the same phone, using the same transfer VMPK.