When I first interfaced with my iPad mini, iPhone 11 and 2015 iPad Pro when I touched the right side of slider 3 or 4 the Pro-4 would shut down and reset changing my settings. When I connected to PUC+ for Bluetooth LE wireless midii it would drain the two AA batteries quickly.
There is an option in the Editor to reduce the LED brightness and when I did that I did not have the problem and could play using IOS without external power.
Turning down the LED made a huge impact on battery drain on the PUC+ so it now an option to use it without external power.