Make sure "enable-stale-production = false" is set in your config.ini (on all nodes).
Thanks for your responsiveness.
So we tried what you proposes, and in order to make it, we had to start a first node with the property to true, otherwise, it doesn't start.
then, we added two nodes with enable-stale-production with false, and we restarted the first node, changing the param from true to false as well.
Then, we tested again, disconnect the network, reconnect the network, and we had the same effect as before.
any other idea?