Found this one tonight:
When creating an IAX phone under "phone" it puts it as "IAX/nnnn-name", while it should put it as "IAX2/nnnn-name" (or at least store it that way internally).
You will notice when creating an "inbound number" under "inbound calls" and pick "IAX/nnnn-name" as the phone to ring that it will create a false entry in inbound_actions.include which reads as:
exten => s,3,Macro(tl-stdexten,IAX/nnnn-name,nnn@default-name)
while it should be
exten => s,3,Macro(tl-stdexten,IAX2/nnnn-name,nnn@default-name)
Correcting inbound_actions.include manually fixed the problem.