In Ukrainian language the apostrophe usually appears in the middle of the word to mark the specific pronunciation of certain sounds. The problem is that the apostrophe symbol («’», U+2019) is probably threated by the search engine as a quotation mark, thus treating the word which it contains as two separate words. For example, the word «xxxxx’yyyyyy», will be recognized as two words xxxxx and yyyyyy. This makes such words impossible to find, and makes totally impossible to give the articles the names with the apostrophe.
This bug was never reported before, because on the keyboard the are some other symbols, looking as and used instead of the apostrophe: «‘», «'», «`», but according to Ukrainian typographic standard, the only right symbol is — «’», U+2019.
This bug doesn’t show up, if instead of the U+2019 symbol the ' mark is used, which is the temporary solution, widely used in Ukrainian wikipedia for the moment. But to keep Ukrainian wikipedia in line with the rules of the language, the U+2019 apostrophe should be processed correctly as well.