Ok, I am writing this in Marketpress since I had this problem only in it (I think this is the only location when you will use Duplicate of WPML....)
WPML have a conflict with Redirection plugin and since they bought are an important plugins I have had to find a fix:
Redirection plugin works on the basis: All post data is correct…
The problem is, it added a single slug copy to the post of the element, and compares it with the NEW slug it created.
The only thing needed to change for the redirection plugin to work with WPML is to unset this slug in dublicate creation (this is the only location where this is happaning…)
so the fix is simple:
on line 3330 of translation-management.php:
Since WPML dont have an action in this location for overide I cannt create a plugin to fix this, I have posted it on bought WPML and Redirection forums and thought I should share it here too.