one brake light out, all others work

And sometimes you can repair OEM switches. When the 4 ways are being used, a lot of current is passing thru the contacts in the switch. Sometimes the contacts will melt into the nylon below the wiper, and then they don't work.This can be repaired without removing the entire sw,with a drop of solder on the contact and then file it flat. Now you might be good to go.
But I don't use the 4-ways anymore on my 68 Barracuda, cuz it's a PITA getting into the switch.
Also should be mentioned that the bulb could be defective, swap it over to the other side. If the issue follows the bulb,replace it,and try again.