RSSI and Zigbees.

I have an Zigbee network set up that has 1 controller 3 routers and 6 end devices. I am getting erratic RSSI readings. I request an RSSI reading ~every 10 minutes. Nothing is physically moving all devices are in a fixed location. The results I get are very confusing. Sometimes I get solid RSSI values say minus 35-50 db. This value may stay consistent for two or more readings, but without fail the devices will start reporting minus 60 and lower. Sometimes they recover but not all at once and some times they never recover the original RSSI. This has occurred even when all devices are within a few feet of each other. I have even had two devices less than 1 foot apart, have one drop it’s reported RSSI and the other stay high for several more reporting periods or have one come back with a strong RSSI and the other never come back up. Sometimes it happens in just opposite they start out all with poor RSSI and after several reporting periods the RSSI steps up to a strong value.

In between these tests I power everything down and start over

What are my options for trying to troubleshoot this issue?

What is the RSSI reported when you have a router in the network? Is it reporting the RSSI from the last packet sent from the end device or the packet forwarded by the router?