What does Geany detect the encoding as when it opens the file?
The `0xF1` is a valid byte in more than one ISO-8859 encoding, eg its `ntilde` in ISO-8859-1. So which encoding the file opens with is pseudo random (its implementation dependent) which succeeds first.
This is why setting the encoding explicitly (`File->Open->More Options->SE&SW Asian->Turkish (ISO 8859-9)`) is available, for when encodings are ambiguous.