For Cyrillic alphabet simbol "є" and "Є" don't work

[Hardline-core]

So in form that you need to write Cyrillic symbol when you type "є" or "Є" pop-up error, and form not go next. This symbol 100% from Cyrillic (from Ukrainian alphabet) but still it didn't work. Other symbol from Ukrainian alphabet work fine. This problem was find on this form https://kobo-ee.nrc.no/single/7aef216b27a25ce9e7bfb5f68a214a88 in field "Тепер ми попросимо вас повторно ввести ім'я цієї людини, але кирилицею. Вам потрібно ввести ім'я ТОЧНО так, як воно вказано в документі, що засвідчує особу."