After updating K2 to version 3.6.3, in the backend, when tried to edit one of items, I got this error:
Error decoding JSON data: Syntax error.
I figured out, that this probably means, that whatever column is trying to be processed by the Registry class has malformed JSON syntax. So far so good, but the debug output does not helped me much in locating the issue.
After checking zillions of pages on Google and trying out couple of solutions which sounded to be maybe meaningful ones, I have finally found the culprit - and the fix.
The explanation was given by one Joomler I highly respect, Michael Babker:
And that was the point of enlightening ;)
The temporary fix was brutal, but effective.
Go to /administrator/components/com_k2/views/item/view.html.php and find this code:
JFilterOutput::objectHTMLSafe($item, ENT_QUOTES, array( 'video', 'params', 'plugins' ));
Replace it with this:
JFilterOutput::objectHTMLSafe($item, ENT_QUOTES, array( 'video', 'params', 'plugins', 'metadata' ));
This solves the problem. Hopefully in one of next releases the problem will be fixed by K2 developers, and you won't need to do this. But right now was for me a lifesaver hack. Don't do it if you don't know, what you are doing!