Without seeing your site, it sounds like you are getting hit with a low-quality content penalty and that's why Google is no longer indexing you.  Adding URLs with Fetch will work in the short run but if the penalty is the cause then I would expect you to see those URLs being dropped out over over time.

Other problems may be indicated by the size of your sitemap file (70,000 entries).  Individual XML files should be capped at 50,000 entries and if your file contains more than that, Google may be petulantly refusing to index.  One way to be sure is to check the server's access log for requests for the site map and see if the Googlebot is still making requests for it.

Google stopped indexing my site. Is there a substitute for a XML sitemap?
I'm working on a website which has multiple admins, some creating contents, some editing and some tagging...

I know editing one node at the same time will cause this error, is there anything else cause this error?

The content on this page has either been modified by another user, or you have already submitted modifications using this form. As a result, your changes cannot be saved.

