Odd brake light failure 2017 - Help!

[Desert Expy]

Hi all,

2017 with LED all around, BCM reprogramed to not alert on bulb out (stops fast flash).

Everything was fine, then it went sideways.

Brake lights on as if the pedal was being pushed, third brake light goes on and off but brake lights dont change. Turn signals work fine all around, multimeter shows 12 to 7.5 on one set of pins and then 12 on the other pins (in the socket)

I have checked the following fuses and they are all good, 13, 14, 18 and 21.

Any ideas what the issue could be?

Thanks!

 

[CowboyPilot79]

I've got a 2015 Expy that just started this. All incandescent though. Forscan reports BOO1 and BOO2 and Brake Pedal all working correctly and in unison, hazards work, blinkers work. I replaced the multifunction switch as well with a brand new one and still only 3rd Brake light functioning.