2019/12/16 22:00:00 [DVR] Starting job 1576551600-59 Bull on ch=[29.1]
2019/12/16 22:00:00 [DVR] Waiting 59m59.970122868s until next job 1576555200-45 BBC World News
2019/12/16 22:00:00 [TNR] Opened connection to 10770EA5/0 for ch29.1 WTTK-DT
2019/12/16 22:00:00 [DVR] Recording for job 1576551600-59 from 10770EA5 ch29.1 into "TV/Bull/Bull S04E10 Imminent Danger 2019-12-16-2200.mpg" for 59m59.970027147s
2019/12/16 22:00:00 [IDX] Generating video index for job 1576551600-59
2019/12/16 23:00:00 [DVR] Marking expired job 1576551600-59 Bull
2019/12/16 23:00:00 [DVR] Starting job 1576555200-45 BBC World News on ch=[20.1]
2019/12/16 23:00:00 [DVR] Waiting 34m59.966157194s until next job 1576557300-55 The Late Show With Stephen Colbert
2019/12/16 23:00:00 [TNR] Opened connection to 10770EA5/1 for ch20.1 WFYI 1
2019/12/16 23:00:00 [DVR] Recording for job 1576555200-45 from 10770EA5 ch20.1 into "TV/BBC World News/BBC World News 1991-03-11 2019-12-16-2300.mpg" for 29m59.966075955s
2019/12/16 23:00:00 [IDX] Generating video index for job 1576555200-45
2019/12/16 23:00:00 [TNR] Closed connection to 10770EA5/0 for ch29.1 WTTK-DT
2019/12/16 23:00:00 [SNR] Statistics for "TV/Bull/Bull S04E10 Imminent Danger 2019-12-16-2200.mpg": ss=100% snq=100% seq=100% bps=13486368,13209632-13493888 pps=1281,1255-1282
2019/12/16 23:00:00 [DVR] Finished job 1576551600-59 Bull
2019/12/16 23:00:00 [DVR] Processing file-701: TV/Bull/Bull S04E10 Imminent Danger 2019-12-16-2200.mpg
2019/12/16 23:00:00 [DVR] Waiting 34m59.114313899s until next job 1576557300-55 The Late Show With Stephen Colbert
2019/12/16 23:00:02 [DVR] Running commercial detection on file 701 (TV/Bull/Bull S04E10 Imminent Danger 2019-12-16-2200.mpg)
2019/12/16 23:14:07 [DVR] Commercial detection failed with exit status 1
Thanks for the prompt clue!
Based on that log, I suspect com-skip was thrown by a school closings chyron that was too large to be disregarded as a logo. It was persistent across all program segments and commercials, leaving no black frames.
Ah yea, weather and school alerts like that are very confusing to comskip.