I have a few bugs about your software.
On iPhone SE 2016 - current firmware, fresh hard reset, no SIM, no WIFI, no bluetooth, installation only pianoscope and Verituner - If I interrupt piano tuning, turn off the display and after a few minutes turn on the device, the pianoscope gets stuck, does not measure anything and helps ejection application and restart the application.
On the iPhone 11 - the current firmware, with SIM, with mobile data - if I want to measure inharmonicity once again, red reacts very badly to green. I have to play each tone 5 times, for example.
Wrong display of information on iPhone SE 2016 landscape mode. The keyboard is very small and octave numbers are only visible from 1/2. see picture on your email