So far my one complaint with the K1000 is the poor dampening. I seem to get more rattles and vibrations when listening to lower frequencies than I do with any other headphones. The majority of listening is fine but every now and again I will hit a frequency that causes resonance and disrupts my listening experience. Aside from that these headphones have a really realistic soundstage and image which is astounding.
Sounds like a problem. I've used the K1000s as speakers (a few feet away) and they never rattled or distorted, not even close.
Check your amp if the rattles are bilateral, or your driver enclosure for any hair or other contaminant if the distortion's only on one side.