T23G Multiple SIP accounts on Multiple SIP Servers

[sjit]

I am attempting to register two different extensions to two different SIP servers.
Server 1 extension 21174 to 192.168.10.30
Server 2 extension 21174 to 192.168.16.10
Both extensions register if they are the only account enabled, they just dont work at the same time.
We are at the beginning stage of changing phone systems and in our plan we require our sip phones to straddle two phone systems for a period of time.
My hope that the yealink phones would have this ability, I have done this / still doing this on a Grandstream phone.
I am simultaneously trying to work through this issue with yealink through there helpdesk.