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public $filters = array ('name'); // filters to apply to when searching for items
it looks like the problem is in this method аnd this is due to the encoding, also possible that this problem is related to server settings...
Eventually, after some unsuccessful attempts to change encoding through PHP, I've discard all changes in this method and at the next day it began to work as expected.
I understand, it sounds strange, but now the filter works with Cyrillic text.