Support

Unfortunately the Categories management is handled by Joomla, not Akeeba Ticket System. If you look at the URL you'll see that it reads option=com_categories instead of option=com_ats, meaning that you are using the Joomla Categories component (com_categories) instead of Akeeba Ticket System (com_ats). This is the standard way to handle per-component categories and Joomla itself is doing that with Banners, Contacts and News Feeds.

So, what exactly can interfere in Joomla trying to save a category? Plugins, namely System and Content plugins. These are loaded by Joomla when com_categories is running and they have the authority to "hook" onto the category save event. When Joomla fires the save event it provides the plugin with something called "context", i.e. which component the category is being saved for. Inexperienced developers ignore that and assume that it's always a com_content (Articles) category. Because of that they make assumptions which do not hold true for anything other than com_content categories (not even for Joomla's own Banners categories!), resulting in errors while saving a category.

Please try disabling the enabled Content plugins one by one and try saving the category to find our which third party plugin is causing this issue. That's exactly what we do when we are confronted with this kind of issues. Then please write to the developer of the content plugin, linking them to this reply of mine so that they can have a clue of what to do to fix their plugin.

There are definitely "system" plugins which could interfere and I believe there could be some "finder" plugins too. Are you able to save categories in other components besides Articles, for example in Banners and News Feeds?

Unfortunately the categories management is core Joomla code so we can't make any changes to it. I can tell you for sure that on a stock Joomla! 3.6.4 installation with Akeeba Ticket Systems I can create and modify categories just fine. The only thing that can possibly intervene in Joomla's com_categories code is plugin. The plugin categories which could interfere, as far as I can tell, are (in order of most to less likely):

• content
• finder
• search
• system
• editors
• editors-xtd
• user

Also please make sure that Joomla and all of its extensions are up to date.

You can always try making a new Joomla installation and install ATS to confirm that the problem does not come from our code if you do not trust my opinion. No offense will be taken if you do that, I understand perfectly. In fact that might be a good way to find out what is causing the problem. Make a new site, install ATS and then start installing the same extensions you have on your site one by one until you find the one that causes the issue.

I understand and I really wish there was a simpler way. The thing is that, unlike our software, neither core Joomla nor third party software is very keen on providing a clear log or stack trace which would let us identify the problem. What actually happens is that a third party plugin has a SQL (database query) error in its code. Which one? No idea. The only clue we get is that Joomla complains about a SQL error. All I can understand from that is that a plugin is causing it. There is no way to trace it back to a plugin unless you try disabling them one by one patiently.

You could of course disable them a dozen at a time to expedite the process. Once you hit the dozen that fixes the problem you will only have to enable a maximum of 11 plugins to find which one is the culprit.

I also note what you said:

I have hundreds of plugins on my site and the Site has been around since it was J 1.5. it made the migration to 2.5 then 3 and so on.

I seriously doubt that all of these plugins are up to date or written to support Joomla! 3.6. The most likely culprit would be some of the oldest plugins (even though there's no way to tell which ones they are, sorry). I also seriously doubt that you need hundreds of plugins. If anything, you should figure out which plugins you really need and remove the rest. Outdated code not only causes functional problems but it could also be a security issue. Abandoned or outdated plugins may have security issues which can and will be exploited by hackers.