Running Channels DVR 2019.09.30.2306 and using the New Guide Database.
Have a couple series passes setup with default end padding of 30 seconds.
I go to the DVR Scheduled list and edit the end padding to 1 minute for a couple of them.
The next day when I look at those same scheduled recordings, it's back to 30 seconds end padding.
My guess is something with the daily morning guide updates is changing the padding back.