Why is my couchapp not displaying on Safari 11.1?

Question

I have a couchapp that displays a graph of my solar hot water system data. It has been working fine on Safari/Chrome/Firefox on Mac/iOS/Android for about 8 years. After updating Safari on my Mac to 11.1, I get the error "This page was reloaded because a problem occurred" and when Retry is clicked, "A problem repeatedly occurred with [the site]". The problem also occurs with Safari on iOS 11.3 (but not before). Oddly, when I open the developer console and reload, the page displays fine and no errors are registered.

Here's the site

I filed a bug with Apple about a month ago but have not received any answer. (39437438).

What could be causing this?

UPDATE: I notice that some static content is briefly displayed before the crash, so it's possible that the error occurs when data is fetched with the jQuery 1.8.1 getJSON call. The code is:

  var url = '_view/byDate?group_level=' + group_level.toFixed(0);
  url += '&startkey=' + makeKey(start_date);
  if (date) {
    url += '&endkey=' + makeKey(end);
  }
  data_query = $.getJSON(url);

Answer 1

This seems to have been fixed in Safari 11.1.1 and ios 11.4. Also I had noticed that iOS Firefox had problems with the site, that is also fixed in ios 11.4