QUESTION: Can't get MCC output to work with known good input about ccextractor HOT 1 OPEN

UPDATE (much closer, but still not working)

Using this https://github.com/szatmary/libcaption which injects 608/708 into FLV files, I was able to get a non-zero-length MCC file from the same source files as above. I'm yet to figure out why though. The file looks valid, but when you play it back the captions are present but the timing is shot. All captions stay up for exactly one frame then move on to the next one. So unless you are an incredibly fast speed reader, you're out of luck. BTW, VLC plays 2.flv and 3.mp4 just fine and the captions are shown at the correct speed.

ffmpeg -y -i HyperDeck_0002.mp4 -codec copy -f flv 1.flv
./flv+srt 1.flv HyperDeck_0002.srt > 2.flv
ffmpeg -y -i 2.flv -codec copy 3.mp4
ccextractor 3.mp4 -out=mcc -o 4.mcc

Improper high speed playback can be confirmed by having ffmpeg convert the MCC to SRT. The srt shows all times at just a counter+33 milliseconds (all captions are just output on the very next frame of video). In all cases, simply changing -out=srt proves the input files are being read, and all timing is being understood. Simply MCC output seems to be broken.

ffmpeg -i HyperDeck_0004scc.mcc zzz.srt

1
00:00:01,104 --> 00:00:03,379
after the off on this event.

2
00:00:03,390 --> 00:00:03,845
Okay. and.

3
00:00:03,856 --> 00:00:05,934
>> But unsolicited Talk about

4
00:00:05,968 --> 00:00:07,349
passwords are hey, summer is

from ccextractor.