If the user stanza name is causing the problem (we don't know if it is or it isn't since we haven't checked) [......]
I suspect that's probably
not it. And i also don't think my suggestion of using a
peercontext option will help either.
What i think is the problem here is that FWD is sending the call to <exten>@<context> - as in this IAX channel format:
IAX/<user>@<peer>/<exten>@<context>Which refers to an extension in a context in the dialplan at the called end. As this context is
iaxfwd and a context with that name doesn't (presumably) exist in extensions.conf, it won't work.
I notice that the default config doesn't put a
context= option into the iax.conf stanza, so adding
context=iaxfwd may do the trick. I don't know if a context option there will override the
context set on the incoming channel, but logic suggests to me that it should.