One of the primary reasons why these devices can pick up so many false alerts on the K-band is because so many other systems share the K-band frequency. For example, most commercial automatic door openers and Blind Spot Monitoring systems utilize this band. So, whenever your system detects this band coming from those systems, it alerts you. But, those are not the alerts that you want to be hearing.
With some advanced technologies that were described previously, these false alarms associated with the K-band frequency can be minimized. But, just be aware that your system may still pick up the wrong K-band from time to time.