@ paul
Looking at the page, it seems the page stops rendering before it is complete. Best guess at this point is maybe PHP is exhausting the memory allocated to it.
Try increasing the amount to at least 128MB. Here’s a blog post which explains how. Different memthods work on different hosts, try starting at the top of the list and working your way down.
Another place to look, look in your PHP error log to see if there are any errors being logged which may helps diagnose the issue. If you do not know where this log is, you can ask your webhost. Every webhost is different so I can’t really point you to where it would be.
Hope this helps, let know what you find out.
ps. I do not believe the is due to the WP 4.7.3 auto update. Both my production and test sites still function correctly. I also scanned the changeset between the versions and did not see any obvious changes which would cause this.
