How about an api_hangup_hook?
Perhaps the aleg hangs up after rxfax but before curl is executed? If the aleg hangs up the remaining extension actions won't run.Looks like you're only using it to indicate a fax has been received? Try using ESL or CDRs. Mod_xml_cdr can post a CDR to a server and will have various variables set that indicate the fax has been received.
Steve on iPhone