Bitrix is ​​not filled in a required field?

Question

1C-Bitrix

Good day to all! There is a feedback form, after sending which I receive an error message saying that one of the fields is not filled. This field is hidden, the value attribute is exactly filled, and the data from this field is definitely sent, but in any case, the $arResult["ERRORS"] array is returned with an error. How can I find a handler for this form that checks the validity of the form and generates an array of $arResult["ERRORS"]?!??