Why can't I find reward seats from Singapore to Melbourne in December/January with Qantas points?

I have been religiously checking the flights, using our Qantas Frequent Flyer Points, on a daily basis since early January this year.
My husband & I are travelling from Melbourne to Amsterdam. Then returning from Budapest to Melbourne in December ‘23/January’24.
I had no trouble booking (using points) to Singapore return on both legs, but cannot, no matter how hard I try, find flights for the Melb-Sing return leg!
I found only 1, flying Jetstar & a 15 hour flight! I am very reluctant to book this flight due to all the hype re Jetstar. And I really to don’t want to spend 15 hours for what is potentially a 7.40 hr flight.
What am I doing wrong?
Is there a trick I don’t understand?

I have made many Rewards Flights purchases in years past, but I am truly stumped now.

I can see at least 2 reward seats in both economy and business for Singapore to Melbourne flying Qantas on December 25 so they are there (might have been taken by someone else by the time you read this).

As we all know, flexibility is important especially during peak periods such as Dec/Jan.

Thank you so much for your help.
We’ll be travelling on the 12th Dec.
I’ll jump on now & see what they have.