@kl3m3n On another, unrelated topic- I use the ESP32 arduino core version 2.0.3-RC1, since it adds support for the newer ESP32C2, C3 etc. This version works fine with the BasicBluetooth demo you provide, and I am using straight Bluetooth for my current project.
However, out of curiosity, I tried to compile the GUI-O_BasicBLE demo. It wouldn't compile. It turns out that I had to remove the existing,older ESP32_BLE_Arduino-master folder from my Library folder. After that ,it will link with the proper BLE library that comes with the ESP32 vers. 2.0.3-RC1 core. Other GUI-O users, who have also upgraded to the latest ESP32 core library, may have the same issue if they have that other, older library installed.
I know, I've googled it.
The Autostart option I haven't found on my phones yet, but I'll keep looking because that could solve the issue.
Yesterday I tried to open Gui-O when the index was at 121, and I found that the App had frozen, but I was still getting the notifications from your script.
I'll turn on logcat and send it to you later, maybe you can see something that will help.