(Apparently this was stuck on your machine for several days....)

So you are changing the tuned frequency for the radio and there is a pause while you are tuning the radio. This is mildly ambiguous to me. Is the display still running but not showing updated data? (That was my interpretation.) Or are you saying that drawing the display pauses until tuning stops?

And very roughly how long is "objectionable."

If the display keeps running but the data is stale this may be unavoidable. The display can lag due to the time the FFT takes to calculate and how long it takes for new data to even reach the FFT calculation. If objectionable is in the 10 ms to 100 ms range for new data to reach the screen as you tune but the display is still updating normally, I am afraid you're stuck with it if reducing "Resolution" on the View menu to "Standard" is not sufficient. Also set the dongle to 2.4 MHz sample rate. If it is longer than that then there is a problem.

If the display completely update stops while you are tuning then Simon has a problem to fix.

{^_^}