If you set Voice Menu in queue then incomming queue’s call will be drop after first position annonce because Asterisk can’t find empty prompt for “queue-thankyou”. For asterisk 1.4.9 the “queue-thankyou” parameter can’t be empty but lastest FreePBX Queue module set it to empty if Voice Menu is set.
the queue-thankyou should be replaced by the sound file you have associated with the ivr that yous specified. I believe if there is a bug it is including IVR’s that don’t have sound files associated with them (not a common thing but I guess it is possible). Check that - because in the configuration I just tested, it puts the sound file associated with my IVR (which is the purpose - the IVR usually says something like 'if you want to break out of the queue and leave voicemail, press 1 now, etc.).
It is replaced only if announcement assigned to IVR but IVR can be without announcement. More that, if you set Announce Position or Announce Hold Time to NO then Queue will be broken because FreePBX set to empty another queue voice prompts. I think that is problem of 1.4.9 version only because developers change app_queue to check EVERY play result.
as mentioned, if there is no announcement with an IVR it is still including those IVRs as a choice, so that may be considered a bug. Feel free ti file a bug against that.
You mentioned a couple of other scenarios - can you articulate clearly the configuration and resulting conf file that breaks Asterisk 1.4 and then specify those in the bug report also - then we can look at putting something there even if it is not being used, to help address Asterisk’s sensitivity to the missing files.