Dishwasher pump is crackling [video]; is it obstructed or does it need to be replaced?
I dismantled the "drain pump assembly" part making the noise and the solenoid and paddle flaps looked fine.  However when manually turning the flaps I could occasionally reproduce the slappy / crackling noise.

Upon further inspection, it was apparent that the seal the axel for the agitator had a small leak.  I ordered a new piece and sure enough, the sound is gone!