Does the plugin have audit trail for sessions when they are created and/or modified? There was a case that a faculty reported that the date time for a session they created was changed. That is why we need to investigate the incident before the blaming game begins.
you should be able to see session_updated/session_added and session_duration_updated events in your log.
I have this course that have multiple sessions: ICS 101, with courseid of 279. But when I check the logstore_standard_log, I can only see one record. See the attached images.
Try changing some other sessions and see what happens in the log if you're not sure. You could also engage your local Moodle Partner to help trace what occurred. I'm also not aware of any bugs that would result in the session time/duration being changed without a user doing this on purpose.