Ok, dans /models/OpartQuotation.php, ligne 960 vous avez ce bloc:
if($this->context->employee){
$cart->id_lang = $this->context->employee->id_lang;
}
else{
$cart->id_lang = $customer->id_lang;
}
A remplacer par :
if($this->context->employee){
$cart->id_lang = $this->context->employee->id_lang;
$this->context->employee->id = 0;
}
else{
$cart->id_lang = $customer->id_lang;
}