Bad Color doppler

Hi guy's!! I have a problem with Color Doppler on SONOS 5500. No errors, boot up OK, but when color flow start, in the box of color, appears a full blue or red... like if it has a lot of gain or can't determinate the velocity flow. (for ex, on the Carotid or Ventricle) Doppler PW/ CW OK. 2D/ MM OK. Help!! Best regards