Import to a 2-level containers tree does not work

All is explained here :
http://www.collectiveaccess.org/support/forum/index.php?p=/discussion/298192/import-to-a-2-level-containers-tree-does-not-work

In a nutshell: importing to a container tree (>= 2 levels) doesn't work
- nothing imported when not required metadata
- error message that have little to do with the problem

Here's the mapping file again, just in case.

Any help would be really appreciated ! I'm quite stucked on that one.

Thanks !