As trmembrino posted above, I tried a variety of canceling and re-creating several problematic scheduled recordings with every record option permutation, all without success.
However, I suspect the problem is more than any EPG change, possibly not arising from an EPG change at all.
These abrupt scheduling failures impact record a few, but not all, schedules of at least four (4) different major networks: ABC, NBC, CBS and PBS.
What is the likelihood that four networks data feeding EPG would abruptly change the same day?
.
Further, I found another troubling PMS behavior while trying to work around the PMS bug or EPG change.
Individual recording options seem to be preserved despite having canceled the associated schedule.
This suggests that PMS may not completely delete whatever database records are associated with a canceled recording schedule and that PMS may be, essentially, preserving any recording schedule corruptions that may occur.
