The scanner does not stop on the right frequency
This is usually due to:
an incorrect setting of the 'Stop On' radio buttons.
Make sure that the 'Stop On' radio button is set to stop on Busy, and not set to stop on Free or None.
a too short a delay for the S-meter.
Check the S-meter has a delay of at least 25 milliseconds. AGC needs to settle after switching to a new frequency before reading the signal strength.
the AGC being set to Slow on the rig .
If the AGC is set to Slow then false stops can be experienced due to the 'remembering' effect of the previous reading.
the 'got a signal' s-meter level is set too high and no signal is strong enough to rise above it
Adjust the 'got a signal' s-meter level on the main screen (just below the s-meter bar)