Not all letters come from the site to Bitrix. How to check?

Question

1C-Bitrix

Good afternoon.
Essence of the question. On the clinic's website on different pages there is a button for making an appointment, when clicked on, one form opens. The form is sent, everything is ok. But, if I go to different pages of the site and send the same form from different sections, then some of the letters come, and some do not. What could be the problem, how to check?