Lock up to me means the wheel stop tuning and you skid to a stop.

What you are describing sounds like and automated panic stop kicking in. You press the brakes to stop and it stops "really hard" harder than you indended.

I think I the system uses the pressure sensor in the brake system to determine when to apply the panic mode. Determined by how quickly the pressure changes not how much pressure.

If there is air in the system that is compressed then stops being compressed so you hit oil, like water hammer in a pipe you could easily cause a spike in pressure that is considered panic stopping.

My money is on this scenario.

It's how my rear brake line split. I hit the brakes quickly but maybe 60% strength. Panic mode took over and put 2000 psi (140 bar)! And split my 17 year old pipe.

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)