Hello. There is no bug in WordPress that would cause this. You are correct. The most current version is what to use. Never modify core files or they will be overwritten.
You site “looked” ok to me but had the following javascript errors.
Failed to load resource: the server responded with a status of 403 (Forbidden)
0WxISPSMfZk.js:60 Uncaught Error: <![EX[["Tried to get element with id of \"%s\" but it is not present on the page.","null"]]]>
glyphs-font-loader.min.js?ver=1.1.5:1 Unable to load fonts.
http://use.typekit.net/c/7d8c28/1w;futura-pt,2,SHB:R:n3,SH3:R:n5,SH5:R:n7;s…870faccc6fc1dd8e42f34a7022d30dcc06ebaa70a141896672eadc51776d2db553014165a1 Failed to load resource: the server responded with a status of 403 (Forbidden)
This is all about your fonts and is probably why you see the problem.
Thanks for this. So is there anything I can do about it? Or is it advanced? 🙂
The problem is with typekit.
There support is at https://typekit.com/help