On my 47 Ford coupe I had this annoying intermittent problem. The front signal lights would light up when the brakes were applied and the brake lights came on. It turns out it was the 4 way flasher switch. It is a Flaming River column. When you pushed in the 4 way flasher switch everything work normally. When you pull the switch out to turn them off everything works properly unless you don’t pull the switch all the way out. It can be pulled out enough to turn the 4 ways off but can allow current to flow into the signal lights circuitry that lights up the front signal lights when the brake pedal is pressed. I wish I could say I am a super trouble shooter but I happened on this solution purely by accident
