When you call the modal window again, does the output format change?

Question

fancyBox

Hello, unusual situation with FancyBox.
The feedback form is displayed in the modal window.
When the call button is pressed for the first time, the specified form goes beyond the modal window, scrollbars appear.
On repeated calls, the feedback form takes the form of a modal window.
scalemodels-tu154.ru/articles/7_4_Tu_154M_RA_85694.htm
What could be the reason for this?