Button not found: In an InputScript I set a radiobutton:

Screen SAPLKEC1.0110
  Set R[Nový výber]        "X"

The name of the radiobutton  R[Nový výber] is exactly as shown in the GuiXT screen elements, but it doesn't work. What could be the reason?

Your SAP system probably runs in Unicode and the InputScript is not stored in UTF-8 format. Since the radiobutton text contains non-ANSI characters the button is not found.