@Andacar If you want to quick test your filename for special (unicode) characters, you can copy & paste it in the Input text box here and press "Identify":
https://www.babelstone.co.uk/Unicode/whatisit.html
Then you can check in the result box, if one of the text characters is not the one you used in the format string.
For example if your hyphen is not the usual
U+002D : HYPHEN-MINUS {hyphen, dash; minus sign}
or your space is not the usual
U+0020 : SPACE
or your underscore ist not the usual
U+005F : LOW LINE
Sometimes even "normal" characters looks like A to Z but are Unicode characters like the Russian (Cyrillic) letters А or В
