Jitterbuffer and SIP transfers

I am using asterisk 1.4.21.2 and SNOM 370s.

Whenever I enable jitterbuffer for SIP calls, the snom 370s loose the ability to reliably transfer calls. Has anyone else had a problem similar to this?

It appears to only happen after jitterbuffer has been enabled for a while, but I could be wrong about that. It could just be something that is fairly rare.