Duplicate creep spawn

[Poxymyr]

So, I just witnessed my spawn giving birth to 2 creeps with the same name, at the same time. The code I use for automatic generation is :

if(!Game.creeps.Worker1) {
    Game.spawns.Spawn1.createCreep([WORK, CARRY, MOVE], 'Worker1', {role : 'harvester', state : 'harvesting'});
}

If that can help, it happens right after my 5th extension was built. None of them are actually used. Both creeps costs 200 energy, but it used only 200 energy. There is one creep that doesn't move, but ages. Object.keys(Game.creeps) only show one of them.

[butcher]

Same for me.

[Avicenna]

Seen it happen a few times as well.

[avdg_]

I'm currently seeing one...

[avdg_]

Since these duplicate creeps stay stuck at spawn, I guess it would easy to write filters to detect such occurrences? Not sure why theses things are happening though...