Steps to reproduce the issue

in all my articles that were created before May 2012 (I am not sure which Joomla! version that would have been) the Json decoding problem re-appeared when I upgraded to Joomla! v 3.7.2 from Joomla! 3.4.8 and with PHP v5.6.30. The front end displays the usual Json error when displaying the article and the backend displays:
An error has occurred.
0 Error decoding JSON data: Syntax error

Those old articles have metadata that looks like this:

{"robots":"","author":"","rights":"","xreference":""}

I cannot imagine HOW it ended up this way.... it is obviously very wrong. NONE of the extensions I have used on the site would have touched the content metadata field, so I suspect that this bad stuff was entered by some prior version of the joomla core. And that means that this is probably not the only site that will experience this problem as they update to Joomla 3.7.2. Oddly, the problem does not occur when viewing the same articles in Joomla version 3.4.8 --- and yes, I checked and the metadata is identical bad stuff.

I was able to get around this for now by changing line line 71 in libraries/vendor/joomla/registry/src/Format/Json.php from
$decoded = json_decode($data);
to
$decoded = json_decode( htmlspecialchars_decode (html_entity_decode($data, ENT_QUOTES ) ) ) ;

Expected result

proper display of article

Actual result

Json error in libraries/vendor/joomla/registry/src/Format/Json.php

System information (as much as possible)

This what I got from my hosting provider - SiteGround
Operating system – CentOS 6.4 (Final) (64 bit)
Apache Version – Apache 2.4 – This Web Server is modified by us
PHP Versions- PHP 5.6.3
MySQL* Version – MySQL 5.6
Zend Optimizer – 3.3.3
zlib/1.2.3
libidn/0.5.6
Kernel version – 3.12.18-clouder0 – This Kernel is our own build!
mod_rewrite is installed

Additional comments

This is a problem that needs to be fixed once and for all in the Joomla kernel. It has nothing to do with extensions of any kind. It makes no sense to penalize people who have been using Joomla for a long time by telling them they have to fix their databases (as was recommended before). This is a Joomla core problem; not a user problem; not an extension problem.