go rogue

(intransitive, originally of sick elephants) to begin to behave in an erratic, uncontrolled, dangerous, destructive, or savage way

(intransitive, idiomatic) to behave in a very unconventional, independent, uncontrolled, or unauthorized way that ignores rules, norms, or expectations

(intransitive, idiomatic) to switch allegiance to, affiliation with, or membership in a country, political party, employer, club, etc. (for example as a spy, soldier, politician, employee, club member etc.)