I just remade from scratch a website for a client, the client ask me to preverve their ranking by making 301 redirect from the original URL to the new URL.

For instance: http://plumber-directory.my-website.com/john-smith-city-1.php became http://directory.my-website.com/plumber/city/john-smith.html

So i put the website online for few days until the 301 partially kicks in the google results. Then the client call me back to tell me that his boss want to switch back to the ancients URLs >_<

So i put a new 301 redirect: http://directory.my-website.com/plumber/city/john-smith.html revert to http://plumber-directory.my-website.com/john-smith-city-1.php

Because google had just few days to assimilate the new URLs, it have now the two kinds of URLs in it's own result pages. Also the ranking of the website keeps falling down every day, i suspect google to mistaking those redirects for duplicate content.

Is there something i can do to avoid a total loss of rankings?