You may want to try out the latest update which disables animation for Safari as well as iPhone because we had issues reported with old versions of Safari before and animation delays.
Second, can you disable font-face and just use Rokkkit or Open Sans Google font and check if the problem recurs? I have heard about missing headings in Safari before and while I could not reproduce them in desktop Safari, I was able to see some issues in iPhone with headings not being rendered (or rather half-rendered with some text displayed and others missing) on first load. A refresh seems to load everything. Pls do update me on this since I am myself having a hard time reproducing these problems on desktop at least. Thanks