Safari only bug: failing to launch angular script (sometimes)

Looking for some advice. One page of my blog is an angular app that is loaded via systemjs. It loads fine in Chrome (and firefox) on my computers and Android phone.

But Safari is very erratic and largely fails to load at all on iOS. Although the systemjs loader is triggered, the rest of the angular code does not start.

After a massive hunt I found that there seems to be a bizarre form of interference from wordpress.

My theme has a javascript file common to all pages (and essentially unrelated to the angular code) that adds events to the navbar etc. Commenting out the wp_enqueue_script that loads this file enabled faultless loading in Safari. I tried simply commenting out all the code in the javascript file (and using an empty file) but that was not sufficient.

I then tried moving the jquery script before and after the block of angular scripts but that had no impact.

I’m really confused. I can’t think of a way that an extra script tag can derail page load for Safari only. Try this link with Safari to see the issue.

Any ideas?