BIND DNS "Forward and Transfer" problems - help needed to debug/trace events.

I have three VBox servers attached to a host only network with a VBox host only adapter and a static IP address and each with its own virtual host. Basically each one is a clone of the other with a unique hostname, static IP address, and (single) virtual host name. Other than that they are identical… I am trying to configure each one to “Forward and Transfer” unknown DNS requests from my VBox host to the other two i.e. to forward DNS requests on if a virtual host lookup is made on the VBox host. This is working between two of them (i.e. a bidrectional dns forwarding exchange) but a third is failing in both directions. Obviously there are too many variables to give a definitive solution but can anyone help me decipher log files. I cant actually see a specific BIND log, which would probably point me in the right direction. How do I start debugging/tracing BIND activity?

urgent assistance required how i may trace bind activity.