Steps:
1) 3rd party SIP app running on Mobile registers to UCM and can make call on corporate network.
Register Call-ID: 39QjZG3VVZ
INVITE Call-ID: 8E~BnPne~7
2) Switch the wifi network to a non-corporate network on which UCM is not reachable.
3) Switch the network back to corporate network, the app re-registers successfully
Register Call-ID: wskCoc1ein
4) Make an outgoing call, UCM complains "503 Service Unavailable” and Warning 399.
INVITE Call-ID: 2ensqmQTFl
Workaround: Admin resets the device from UCM or wait till old existing sip session expires.
SDL log attached.
