Steps to reproduce the issue

Install staging or nightly build.
Install the French language.
Set French as back-end language.
Create an article which title contains some Greek and Cyrillic letters, leave the alias field alone.

Choose the characters among those which are transliterated by the French custom transliterate method, i.e.

public static function transliterate($string)
		{
		$str = JString::strtolower($string);

		// Specific language transliteration.
		// This one is for latin 1, latin supplement , extended A, Cyrillic, Greek

		$glyph_array = array(
		'a'		=>	'a,à,á,â,ã,ä,å,ā,ă,ą,ḁ,α,ά',
		'ae'	=>	'æ',
		'b'		=>	'β,б',
		'c'		=>	'c,ç,ć,ĉ,ċ,č,ћ,ц',
		'ch'	=>	'ч',
		'd'		=>	'ď,đ,Ð,д,ђ,δ,ð',
		'dz'	=>	'џ',
		'e'		=>	'e,è,é,ê,ë,ē,ĕ,ė,ę,ě,э,ε,έ',
		'f'		=>	'ƒ,ф',
		'g'		=>	'ğ,ĝ,ğ,ġ,ģ,г,γ',
		'h'		=>	'ĥ,ħ,Ħ,х',
		'i'		=>	'i,ì,í,î,ï,ı,ĩ,ī,ĭ,į,и,й,ъ,ы,ь,η,ή',
		'ij'	=>	'ij',
		'j'		=>	'ĵ,j',
		'ja'	=>	'я',
		'ju'	=>	'яю',
		'k'		=>	'ķ,ĸ,κ',
		'l'		=>	'ĺ,ļ,ľ,ŀ,ł,л,λ',
		'lj'	=>	'љ',
		'm'		=>	'μ,м',
		'n'		=>	'ñ,ņ,ň,ʼn,ŋ,н,ν',
		'nj'	=>	'њ',
		'o'		=>	'ò,ó,ô,õ,ø,ō,ŏ,ő,ο,ό,ω,ώ',
		'oe'	=>	'œ,ö',
		'p'		=>	'п,π',
		'ph'	=>	'φ',
		'ps'	=>	'ψ',
		'r'		=>	'ŕ,ŗ,ř,р,ρ,σ,ς',
		's'		=>	'ş,ś,ŝ,ş,š,с',
		'ss'	=>	'ß,ſ',
		'sh'	=>	'ш',
		'shch'	=>	'щ',
		't'		=>	'ţ,ť,ŧ,τ,т',
		'th'	=>	'θ',
		'u'		=>	'u,ù,ú,û,ü,ũ,ū,ŭ,ů,ű,ų,у',
		'v'		=>	'в',
		'w'		=>	'ŵ',
		'x'		=>	'χ,ξ',
		'y'		=>	'ý,þ,ÿ,ŷ',
		'ya'	=>	'я',
		'z'		=>	'ź,ż,ž,з,ж,ζ'
		);

		foreach($glyph_array as $letter => $glyphs)
		{
			$glyphs = explode(',', $glyphs);
			$str = str_replace($glyphs, $letter, $str);
		}

		return $str;
		}

For example test with æβģя which contains a Greek letter (β) and a Cyrillic one (я)
Save the article. The alias field contains, righfully aebgja.

Now, empty the alias field and test again.
You will get ae-g which corresponds to the Core default transliteration (Core only take care of latin characters)

Now, change the title, empty the alias field and use ONLY Cyrillic or Greek characters for the title (still from the list above), for example: Ολοκλήρωση.

You should get oloklirori but you get a date 2017-06-25-14-58-03