Both PCs are running Arma 3, not the Dev version.
Only spawnGroup Units are created twice, the editor placed units are fine.
Chat-Triggers that check the death of the spawned units are triggered locally, so I see "..." when group1 is dead. And the other pc sees the same "..." when the "cloned" group1 is dead.
Triggers for both players being in a certain area at the same time work perfectly and immediately.