I want to use transfer_on_fail to transfer the leg to another extension, i do this by setting the failure_causes and continue_on_fail to false (because of https://github.com/signalwire/freeswitch/blob/master/src/switch_channel.c#L4972 it will not work if set to true).

that works, but i ALSO want to use continue_on_fail, how can i do this? i only want to be transferred if cause is busy.