My lights like to flash every now and then. Ya I was going to check that connection it was next on my list. I replaced one pigtail ground was no good. The flashing isn’t the alternator either. I have replaced the switch. As for parasitic draw I narrowed down the circuit but I think it could have to do with some random house wiring the previous owner put in for the brake lights. Battery dies after like 5ish days so it never really bothered me to dig deeper.