Maybe the rotor alignment bolt was not tightened properly?
Did they use the air drill to wrench the bolts back on or did they torque them to spec by hand?
Check tire blanacing, and for warped rotors.
Water on a hot disc can warp it.
Perhaps your ABS sensors are dirty and are kicking int he abs.
Check the rear brakes, and also check for any bad suspension bushings.
I hope that helps, I'm not a tech, but that list shoudl just about cover it.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.