Brakes groan and pull away a little after doing work

Bah.. well I tried to do my bearing today (got stuck on upper ball joint that wont come out, fml) and after putting everything back together and heading home, my brakes seem to give a short groan and it feels like they lighten up/pull away for a split second and comes right back. I feel it in the pedal as well. This happens while braking through the 2-4mph ish point.
I don't have a ton of knowledge on the system, but I did remove my ABS plug and the hole was open while doing the work, there was a bit of dust/dirt going around.. Could it have gotten contaminated and the ABS system is acting funky now? I tried cleaning the actual ABS sensor and the magnet at the end before seating.