This could be normal ABS operation. On rough pavement, a wheel could momentarily stop turning and cause ABS to engage. The thing to remember is that when the ABS engages (you'll be able to feel it in the brake pedal, and can probably hear it as well), you should continue to press harder on the brake pedal. If the ABS engages under light braking and you don't depress the pedal any further because the ABS has engaged, you'll never be able to slow the vehicle any faster than you're currently slowing. But you can still press harder and slow the vehicle more, especially if the ABS is only modulating one wheel. It will continue its work and modulate that wheel and will begin modulating other wheels as necessary. It's now been about a year and a half since I've moved into an ABS vehicle and that's one of the things to which I've had to adjust.
If you're not sure, you should definitely take it to your local dealer, make sure they are able to duplicate what you're experiencing (even if this means riding with them), and let them determine what's actually occurring.