Code Change is typically seen after an upgrade, it's supposed to mean the firmware has changed, but I've seen it in normal operation as well. Nothing about these logs concerns me.
I would pull the logs and look for any old, archived logs, but my guess is they didn't get written to disk because something went wrong. Typically in this situation I would run live log captures and continue normal operation, if it recurs you have the logs, if not just write it off as a fluke.
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