Very strange. In troubleshooting this I'd pick a CRA to test, then set digit translation for an unused digit to go right to an ext on another node. Call the CRA, press that digit, see if it transfers correctly. It sounds like for some reason the CRAs can't access the trunks to the other site. Voice mail is UVM, I presume? I'd also inspect the System/Devices?Node IP Connection Groups, make sure OUTGOING ACCESS is PP051 Auto All Stations (or whatever PP number yours is), then click on the phone icon for PP051 to be sure you see all your CRAs listed there. If the CRA is not in the list, it can not use the connection to the other site and transfer will fail as busy.