The AX error message is due to the server receiving an invalid response from another server and the cookies / cache on the browser are outdated.
If your browser history, cache, and cookies have not been cleared for a while, the browser will use old data to load the website which is why the error surfaces when moving around in Dooap regardless of the page you are on.
To resolve this, go to the browser being used (preferably Google Chrome) and clear the history, cache, and cookies for 'All Time'. This will prevent the error from popping up again in Dooap.