Question about App.focus() behavior

I would ask a question about a problem I'm having related to App().open() and App().focus() methods:

I have a code to open an application and focus similar than this one:
executable = App(executablePath)
executable.open()
wait(3)
executable.focus()

Sometimes the executable doesn't run. I can see in the log of the App().open() and App().focus() this text:
[log] App.open [8860:Executable_name.exe]
[log] App.focus: [9692:Executable_name.tmp]

When the executable is properly launched, I can see that both App.open() and App.focus() return the name of the executable with ".exe" extension. My question is, why the App.focus() method return the name of the executable with extension ".tmp" when it doesn't work? What is happening?