Modal window closes after a second?

Question

Joomla

There is a site lozhki-luzhniki.ru on Joomla 2.5. The customer needs to make a pop-up callback form on it using the "Order a call" button at the top of the site where the contact phone number is. Made on fancybox, this script worked on my test site (a simple site with Bootstrap). On this site, when you click on the button, a window appears for a second and disappears. What could be causing this problem?
PS Ready-made modules like CallMe are not advised, you can't arbitrarily insert them into the page.

Answer 1

<a href="#callback" class="button fancybox">Заказать звонок</a>

change to
UPD: not true
Pressing this button calls a function that hangs on the entire header (when pressed), the window does not disappear but the page is updated