Roadrunner drives me crazy

Hello. Can someone explain to me why exactly after 30 seconds I hear the Beep Beep of the Road Runner?

Thank you very much to those who can help me understand what is happening.

Footnote: I have attached the mp3 sound that the "call Sound1.Play" command is executing to this blog entry so that you understand what I am saying.

Bip! Bip!

you are playing the sound in a Timer. Is the timer enabled? have you stop it after play the sound?

Yes, the timer is always enabled.
Why should be neccesary to stop it before play the sound?
Sound is played only when "Listado" is empty (inside the "if")
The problem I can't solve is how exactly works "BluetoothLE1.DeviceList"
Thanks for your answer.

Then you need to check why the Listado.Text is empty.

Exactly. But the Big Issue is Why Listado is sometimes empty and sometimes isn't. Why?
I can't establish a pattern. It seems as "BluetoothLE.DeviceList" doesn't always have the same answer.