Thank you Saguaros but ERROR CONTINUES.
To reproduce, run JA Multilingual on any Spanish content on above test site.
Firstly, upon conclusion, translated articles are NOT checked-in.

Secondly, after checking-in the article(s), you still get a 404 error.
• To manually fix, you need to go into every translated article:

• Check the Preview of Translated Article:

• Save the Article Manually and Clear Cache:

And you fix the 404 error.
Thanks and regards,