support told me that I might have an issue with my Z-Wave devices as one of them might be too far and not close enough to a repeater for example. I would like to add a repeater but I need to know what device is having an issue. I have a C5 hub, and I'm not sure where to find that information.
Without any tools, it's trial and error. You could build a zniffer to see what is going on with your z-wave network. Here is the link. They're pretty easy to make. that's the most economical way anyway.