I had a similar issue with that, for this line:
Redirect 301 /about-us http://www.newsite.com/about-us <------- directs to http://www.newsite.comabout-us
you could go to your newsite.com htaccess file and write a new htaccess line:
Redirect 301 http://www.newsite.comabout-us /about-us
the idea is write your rule first on the old site , then if that redirection fails, go to the new site htaccess file and write that error URL and correct it there.
this worked for me on some urls that i just couldnt figure out why they were wrong after spending lots of time trying different htaccess tricks.
i now this is not the cleanest way to do that, if someone finds something better please reply to this thread.