All 4 brakes locked up???

[Milehighbmw]

02 x5

Like the title says I had all four brakes completely lock up as I was driving. By the time I got pulled over off the highway they were all 4 smoking.

I was having a problem with the brake light switch under the dash. It somehow gets pushed in occasionally to the point the pedal no longer makes contact and the brake lights stay on. I went home grabbed tools. Put it in neutral to see if it would roll as I was on a hill. Nope not at all. Got under the dash fixed the switch started it up brakes released drove it home.

Later that evening decided to try taking it on a short errand. By the time I got down the block they locked again. This time the brake light switch was still making contact. I got out and pulled the vacuum line and check valve from the brake booster. There was a loud release of pressure. Plugged it back in brakes went back to normal. Drove it on my errand and back home no problem.

I assume this isn't fixed and I'm stumped bad.

Codes from inpa were for pressure sensor, brakes overheating and brakelight switch. If I remember right. I'll post them when I get home later

Any ideas?