So, i have found the right solution. Recaptcha v3 uses decodeURIComponent function to work with urls, so it can't decode urls (throwing an error 'URI malformed'), that were encoded with URI-encoding. Now i use encodeURIComponent for generating my urls and everything works good.
For example, encoded russian letter 'ю' with encodeURIComponent is "%D1%8E" (while it is "%FE" in url-encode)
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