Instability with Zigbee network after few hours of operation

Guys,

Here is my configuration:

- 11 Nodes all configured as routers (all sending out reports to Gateway)

- Implementation is based exactly off Sensor Demo application.

- Stack is 2.4.0-1.4.0

- All nodes seem to be storing nwk info in NVRAM.

During reset entire NWK comes up. All nodes respond and I get desired data. After few hours of operation the whole network becomes unstable in that, some nodes stop sending data and others keep sending data, but I see a lot of "Route Req" and "Match desc Reqs" going around in network. See below for a snapshot. The basic questions I had are:

- Is that a healthy sign that every few seconds one "route req" and "match desc" gets generated? I do not understand why is this happening especially if that router is already successfully sending data to gateway. I understand such requests if they are from disconnected nodes.

- I took one node from this network and tested on bench. I found it was generating many "Route Reqs" along with sending partial data after dropping few packets. Even after turning it on/off. Apparently when I flashed a new FW, it stopped sending such flood Req. and in started responding neatly to gateway - only few Rout Req initally- after that none.

I was suspecting, this node along with few other nodes in earlier network went stale. But still I do not understand why and how did this happen?

Any clue what is going on here?

(This snapshot is after few hours of NWK formation)