Thanks for the informations
Even though we switched the kernel to the x64 version, it still appears as a x86 kernel (see image_kernel-1).
In the editor, we can see that the kernel used is the x64 (see image_kernel-2).
But we noticed that in the boot menu of the active task created, the kernel used is still the x86 version (see image_kernel-3).
Maybe there's a bug keeping the active tasks from gathering the right informations about the used kernel ?