I don't think my wind speed is reporting correctly. What can I do?

The Issue could be the impeller or the unit itself.

Pop out impeller and then reinsert to see if issue resolved.
If not, go get a magnet. A refrigerator magnet is fine.
Pop out the impeller and put Kestrel display screen on Wind.
Move magnet around impeller area and take note of any wind reading.
If a small wind reading appears, impeller is defective: replace the impeller with a new impeller from ExtremeMeters.com.
If no wind reading appears, unit is defective: send unit into NK for repair.