Painless wiring brake light gremlin

Similar conditions have occurred in all types of vehicles with 1157/dual filament bulb fixtures. More common condition is turn indicators, etc.. coming on with park lamp circuit. That fault is always lack of chassis ground at front park/turn fixtures. You should check/prove chassis ground at all front and rear 1157 fixtures.
If park lamps circuit can find a chassis ground path through the turn circuit, brake lamp circuit could find a ground path through park and/or turn.