Made 3 batches this year. This was batch 2, the most melt-in-your mouth batch!
I'm not sure what caused the difference, but I used different brands of flour for all 3 batches since tapioca flour was out of stock at the supermart near my place.
This was the brand I used for batch 2, bought at the NTUC near Scape.
One key difference in the dough was that batch 2 was a lot stiffer and harder to roll out. I recall that it was similar last year too - the harder it was for me to roll it out, the more melty the cookie.
Another difference was that batch 2 had little designs on it. I forgot about them in the other batches.
Gotta find some way to gain consistency!