Kim,

I think there must be something else wrong in your scenario. In my understanding and also according to wiki (which as we all know knows everything)

call setup will fail for surplus devices

That is, in your scenario only 4 of the calls should ultimately alert. I have to admit that I never tried it really so I might be wrong, but alerting the devices without having at least one channel available doesn't make sense to me too.

I suggest that you create a support ticket for this.

Christoph