Please, before giving this raw alpha, provide old beta availability next time, which was better. Don't make it too advanced, lumpy and slow, wiki has all tools needed to work on text don't duplicate functionality: Add possibility to publish page to private space where user WILL be able to work on with standard tools. e.g. User:Foo/Translations or User:Bar/Draft (i did it before, now it gives Error converting HTML to wikitext: docserver-http: HTTP 400 error). Current editor is slow, crushing and work is really frustrating. NB: cellphone is to ring, translator is to translate so stop over there.
Topic on Talk:Content translation
ContentTranslation tool is in use by several translators and is available as "optional" Beta feature since last 2 years in all Wikis.
Regarding your particular issue, please provide source and target languages you used and article name. I tested publishing in User namespace at, https://gu.wikipedia.org/wiki/%E0%AA%B8%E0%AA%AD%E0%AB%8D%E0%AA%AF:KartikMistry/%E0%AA%AD%E0%AB%8B%E0%AA%B0_%E0%AA%98%E0%AA%BE%E0%AA%9F and it seems working fine. Also, if you're getting any other errors, let us know. We are here to help!
Yup, I publish all of my translations to my user space, so it's definitely possible. You can now even change the destination during the translation process (just click on the title of the right column). And specify, say, User:Alex Khimich/Something here.