I have several of these and I'm not having any issues. If these are the only zwave devices you have your network it may not be a strong enough zwave network to support much of a separation. Try putting them all in the same area as your hub to see if they will stay connected. If they stay connected while in the same area you may have to add a few smart plugs to use as repeaters to get the zwave coverage you need.
It looks like you're going to have to wait for the return call from support. You may have an issue with your hub's internal zwave module. One other thing you could try while you are waiting is standing your hub on its side (assuming you have it laying flat).
Thanks Terk. While I don't have any other non Iris z-wave items you got me thinking. Here is what I did and it has been almost 3 weeks and no disconnects. I went and pulled all my smart plugs from outlets. I then made sure all smoke detectors and other battery devices were connected to system. I then did a z-wave rebuild. I then started adding smart plugs 1 at a time back into original outlets starting with the center of the house points and did a z-wave rebuild after each install. I figured by doing this I gave my most troublesome detector (basement) a 1 or 2 hop route back to hub. As I added more smart plugs to perimeter of house it should give multiple 2 or 3 hop routes back. So getting back to your post, maybe I had a flakey signal from one of the smart plugs messing up the z-wave network and a TOTAL rebuild versus just moving a plug here and there did the trick.