[Foreground] Navbar broken and page width too narrow

Hi

I installed Foreground skin v2.1.0-alpha on my MediaWiki site with version 1.30.0, but the navbar seems to be broken into three rows, and the page width is too narrow. However, when refreshing the page, everything appears ok for one second, then it immediately changes to the broken style.

Any idea why is this happening?

URL: http://www2.mhbk.org

Thanks.