Found this article quite helpful
www.australianfrequentflyer.com.au
I was getting a "central database" error (4002 [7597]) when trying a multi-city booking and it told me enough to know I needed to call.
I was on the phone with the lady in the call center for a bit over 3/4rs of an hour, but she managed to get the Emirates Z tickets to come through eventually.
From the comments she made it looks like there was a handshaking / timeout problem with the Emirate booking system that with patience she was able to work through.
Waived the fee for assistance as well.
Not something QANTAS IT can really make go away, though they could certainly give a better error message.

Qantas Website Error Codes (And How to Avoid Them)
We've put together a list of the most common error codes that you'll encounter on the multi-city booking page of the Qantas website.

I was getting a "central database" error (4002 [7597]) when trying a multi-city booking and it told me enough to know I needed to call.
I was on the phone with the lady in the call center for a bit over 3/4rs of an hour, but she managed to get the Emirates Z tickets to come through eventually.
From the comments she made it looks like there was a handshaking / timeout problem with the Emirate booking system that with patience she was able to work through.
Waived the fee for assistance as well.
Not something QANTAS IT can really make go away, though they could certainly give a better error message.