Thank you for getting in touch.
In a case like this when the plugins are not functioning as intended we recommended that you disable the non-toolset plugins.
What this means is that you will need to go through your list of plugins and disable each of your plugins one at a time while checking to see if the issue still remains.
If this doesn't work . Would you mind allowing me to have admin access to the website so that I can have a more detailed look at this for you ?
Please where applicable please provide me with a link to an example page where I can see the issue.
I've enabled the private fields for your next response.
I had a look at your debug data and noticed that your mysql version is below the minimum requirements. Currently you have version 5.5 but we require at least 5.6
At this point I would recommend that you remake the content template for the post.
The reason being that i've gone through the basic debugging steps and they have yielded no feasible results. The content template is still unable to be updated even when the plugins have been disabled and theme changed.
I also took a copy of your site to ensure that it wasn't an issue with your server causing the problem but the issue still remains even on the copy.
The conclusion here is that the template could've been corrupted somehow when the most recent save was done and as such I recommend remaking the template.