Checking your two jobs i can see there has been an upgrade to Syncsort.
Your job on the 17th used Syncsort 1.4
WER169I RELEASE 1.4 BATCH 0520 TPF LEVEL 2.0
On the 20th 2.1
WER169I RELEASE 2.1 BATCH 0539 TPF LEVEL 4.1
Apart from much bigger allocated sort work space i see this message on the 20th
WER813I INSTALLATION OPTIONS IN MFXPRM00 WILL BE USED
that is not in the job on the 17th.
It is likely that these parms have turned off the use if Ziip by syncsort.