Search works incorrectly if the request contains specific ukrainian and spanish letters

The list of Ukranian letters: ї, є, ґ
The list of Spanish letters: ñ, á, é, í, ó, ú

1. Go to any topic, type any text containing the specific letters from the lists above.
2. Type the text from Step 1 on the Search field, press Enter
AR: No results found Message is shown.
ER: Search should work correctly and return the valid results

The same problem occurs with specific letters of other alphabets.