“Send” button is shifted to the left

Hi, I am using your plugin for about 2 years and several months ago I noticed that my “Send” button in contacts form is shifted to the left for some reason. It wasn’t like that before, but I don’t remember, when exactly it started.

When I reload page, the button appears at first in center. And a moment later it “jumps” more to the left. Even though my contact form is centered in code.

Here is a screenshot – https://c.radikal.ru/c13/2105/c7/ebc978ccb4b3.jpg

I wonder how to fix it?

Just in case, I attached link to my “Contacts” page.

Thanks in advance for an answer!

The page I need help with: [log in to see the link]