Hi Smanar,
Thanks for the reply.
So, I misunderstood the sleeper setting.
I thought sleeper suggested that it was an end point that doesn’t periodically provide status information. 
Since the SNZB-04 only seems to provide status changes, it can go silent for some time.
The binding part is not totally empty for snzb-04, but the ias zone doesn’t include any specific attributes.
Any thoughts how to prevent the disappearance of devices from the network?