That 20V signal on the log looks too "smooth" to be anything related to forces external to the ESC.

Bad solder joints, pitted connectors or wonky cells wouldn't give a line as straight as that, although there is a small bit of ripple in the middle where a bit of curren tis being drawn.

My guess is the ESC at some point decided the voltage was 20V for whatever reason, logged it and acted accordingly.