my crosswave is making a horrible grinding noise, sounds like it's eating rocks

Yeah, this one's common. Something hard is jammed in the brush roll.

1. Unplug the machine immediately to prevent motor damage.
2. Tip it back onto its rear wheels.
3. Manually spin the brush roll by hand. You'll feel the obstruction.
4. Use pliers or a similar tool to pull out the debris (common culprits: hair ties, coins, gravel).
5. Spin the roll again to ensure it moves freely.

IF THAT DIDN'T WORK: The brush roll itself might be worn out or the bearings damaged. The brush roll is a consumable part not covered by the 3-year warranty for normal wear and tear. You'll need a replacement.

HEADS UP: Always do a quick visual sweep for large debris before cleaning an area. The machine is for surface cleaning, not picking up Legos or pebbles.