Firefox edit problem

HI, Have a weird problem. I can not edit orders when using Mozilla Firefox on opencart 2.0.3.1 It works fine on Chrome, IE, Safari. Reading the forums for the error I receive shows problems and fixes with API or Http vs Https but that is for not being able to edit on any browser. Anyone know why it would be just Firefox? Thanks in advance. This is the error but only on Firefox

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

OK

<b>Notice</b>: Undefined variable: json in <b>/home2/xxx/public_html/vqmod/vqcache/vq2-admin_controller_sale_order.php</b> on line <b>2623</b>

Works perfectly on Firefox for me. Might be your local issue, especially considering that error is in modified version of the core file.

Thanks for response. It references the last line in that file which is $this->response->setOutput($json); } So you think it is maybe a setting in my browser on my local machine? I can use Chrome but I do most everything on Firefox so wanted to get that working

Chrome can simply suppress the error (I don't use it, so not sure), but it's still out there. Firefox displays it to you and it's good, because you're aware, that something's not right. Now you just need to find out, what exactly is not right.

Thanks. I just did a beyond compare with the stock and the modded one. Most of the mods are made by ajax order editor contribution which works in Firefox for most things needed to edit ie quantities etc. Makes order editing easy other than adding different products or completely removing them . I think I will check through that first since that may be causing the issue. Will remove and see if problem goes away. Whatever it is also makes it so I cant delete orders in admin on Firefox but that does not throw an error it just says it did it and doesn't . But I Can delete on other browsers.