asterisk users - Sep 2004 - Monitor w/ m flag - Doesn't mux in some cases - Advice?

I'm currently using the Monitor option w/ the m flag for every incoming
call and every outgoing call.  I simply have it as priority 1 for
inbound and outbound.
 
If someone calls in and we transfer that call to, for example... Another
phone number (not extension).  The call is still recorded except it
doesn't mix the two sound files together.