Self-cancel not in log?

I have a pipeline that sometimes does a self-cancel. (See other nearby posts for why).

However, the self-cancel doesn’t end up in the log. I presume this is because the process chain took a signal, (TERM, KILL, whatever), while those lines were in buffer somewhere.

Is there any way to force the buffers out before the kill? Or to make sure they get flushed before the process dies? Or better, to determine why/how a pipeline was killed?