I’ve used MODX for a long time for my websites and I also use Content Block very much. Recently I’ve transferred my MODX installation to another hosting.
Since then I have this really weird problem, when I try to create an Content Block-Layout everything works fine. But only when I an “select” option to the layout, I cannot save the layout or anything. The same thing applies to editing an existing layout.
In the developer tools of the browser, can you change to the “Network” tab to check what request returns the 403 error? What is the “action” parameter of this request?
I don’t think “Saving” is the problem here. It looks like one request to the ContentBlocks-connector returns an unexpected result that “breaks” the Javascript.