Virtual screens, app initialize

Hi, I created an app to connect with a small robot using Bluetooth. I have been testing the app since 3 months ago and today I discover a different behavior. When I press the middle or home button, the app minimizes. Before, when I resume the app it displays the virtual screen where it minimizes and Bluetooth connection remains.

Now, when I resume the app:

  • The app initializes.
  • Shows the main virtual screen, as programmed in the initialization.
  • The device is connected to the robot's Bluetooth, but I can´t send any command, reconnect or disconnect. I have to reboot the robot. (Sending command shows Error 515)

I tested with this code:

Has something changed on the MIT app inventor components?