I have noticed that on all iP11 + iP SE 1st gen + iP SE 2020 devices when tuning C7 the sensitivity is too low. Only this one tone. The strobe only responds with a delay of about 3-5 sec. You turn the tuning pin and the strobe shows the same thing over and over and only after 3-5 sec does it change.
No need to explain the procedure to achieve this. Every time you tune on every piano. Try it yourself on your piano.
Have a nice evening Milan