I've just been advised by the boffins that this release needs a couple of tweaks to the SIP trunk config to avoid possible issues with outgoing calls. Do this for all SIP Trunks/carriers and test.
a> Set the min. reserved call license to 0, on the basic tab of the associated SIP Peer Profile.
b> Do NOT set overlap out-pulsing for any routes for SIP trunk. ie. "Digit before out-pulsing" should be blank.