Just like the title says, it is unregistering after 30 minutes. It initially registers fine and everything works great. Then after 30 minutes it unregisters and this shows up in the log "Ext.3333: a contact is unregistered." This is happening on two different Yealinks from two different remote locations. Weird thing is from the same locations an SPA504G and the 3CX softphone both work fine. Any ideas?