The upgrade paths were always tricky, 11.6.2 has some PREUPGRADE requirement COP files but 11.6.1 does not have them and the upgrade guide lists 11.6.X to 12.5 SU3.
You can always open a TAC case to verify the COP files that you need and the correct path. In the past, I have done 2 upgrades (listed below) for safety as I didn't want it to jump too far.
11.6.1 > 11.6.2
11.6.2 with needed COP files (2) > 12.5 SU2+
I hope that helps