Why doesn't Firefox render flexbox correctly?

Question

css

Now I'm designing a site, and there was a problem displaying flexbox in Mozilla Firefox, everything is fine in other modern browsers.
Here is the site: clients.tapata.ru/juice
Here is how it is displayed in Chrome:

And here is how it is in Mozilla Firefox:

*All browsers of the latest version
I use S-Grid for layout: https://github.com/juliancwirko/s-grid

Answer 1

Solved the problem by changing the variable in the s-grid settings
from base-font-size = 14
to base-font-size = 16

Answer 2

This is due to the margin in .header--logo

Answer 3

It's too early to use flexboxes now.
We have to wait a year or two.