Locked OSF Brake!

[Alluminio]

All has been quite well with my A8 D2, which I purchased in November 2013, apart from a couple of niggles, and a new front brake calliper and suspension arms fitted in November 2014.

Yesterday something more dramatic happened; the OSF brake is locked on.

All was working well until I went out in the snow and ice and enjoyed a little bit of spirited driving, and thus the ABS and TCS were in action a few times. All was well until the ABS was activated as I approached a junction and then made left turn to stop at a garage. After restarting to leave the garage, the car felt as though a very effective parking brake was on - which it wasn't.

Lifting off the throttle made the car lose speed very rapidly and as I reached home about 2 miles away, there was smoke from a very, very hot OSF brake.

The NSF brake calliper was replaced as the piston was corroded, but it never fully locked. Up until yesterday there was no sign of sticking on the OSF brake. The car has only a genuine 73K miles on it and until the recent calliper, all the components on it as it left the factory.

I am wondering if the ABS unit may have a jammed valve, given that until yesterday, my usual driving style means I can't ever recall the ABS of TCS having been previously activated!

There are no warning lights illuminated.

I have a fully-blown VCDS to interrogate the car's systems, and whilst I will be doing this later today when the temperature rises, I wonder if anyone else has had this situation?

TIA

Mark