Yeah looks like it's a typo in the CSS. There's a unitless height value that's generally ignored but causes problems for some browsers apparently. A fix should go out in the next deploy, but in the meantime you can apply a local style to fix it (for the curious)...
Do you have Proxima Nova installed locally? The font stack does look for a locally installed version of the font first - it looks like it's applying the 900 font weight instead of 600.
I think you'll probably want to remove those font-size adjustments and re-assess afterwards. You'll find that the majority of the redesign is indeed sized with ems, including all text sizes. You'll also want to adjust #header_wrapper to position:absolute if you deice that you're not going to use the settings to disable the fixed header behaviour - setting static without adjusting the settings will be unpleasant. To be safe, in case you want to play with the header settings later, you probably want to actually make that selector `.set-header--fixed .header-wrap { position: absolute' }`
.page-whatsnew .site-wrapper--static, .page-whatsnew .content-wrap, .blk--whatsnew { height: auto; }