Hello, i come back here because i finally managed to find why load don't works.
2 reasons :
Firstly, we have one nms recipient schema extension.
And the schema contains an high level <element> that contains all attributes for that schema extension.
Wich result on the following appereance on the tool request. (white square)

And so this "free element" prevent the mapping tool to suceed when load is called.
The second issue concern the link element "revcardinality", if you use "single" and the relation with id does no exists then the load operation crashes.
I hope that could help someone one day,
Thanks you all for your help !