End Node Registration fails (sometimes)

Good morning,
I have simulated a PAN in the lab with a coordinator identical to the one in service on the field, for testing and repair purposes.
The lab coordinator is configured exactly in the same way as the field one.
When I take a field end node to the lab it does not register to the lab coordinator as the lab and field 16 bit operating PAN IDs are different.
However, the association indicator AI is 00, signaling that the end node is registered, although actually it is not, as it can not communicate with its (lab) coordinator. The device does not try to de-register and register again to obtain a correct operating PAN ID (16 bits)
Is this a bug of the device or am I doing something wrong?
Thanks to anyone that will give me a help!

No that is NOT a bug. You need to issue a Local network reset on your device you are bring in from the field. That will allow it to Associate to the New network that is in the office. When you bring it back out to the field, you will need to do the same thing.

Your alternative to this is it is configured as a Router is to use the Watch Dog timer (NW) command. https://www.digi.com/resources/documentation/digidocs/90002002/default.htm#Reference/r_cmd_NW.htm?Highlight=NW

OK, thanks for your answer.
But the fact is that the association indication is 00, which means “device associated”, although it is really not.
This is misleading, or am I wrong?

It means that it was associated at some point. It does not mean that the network is still in range. That is what the NW command is for.

I see, so the association indication 00 means that the device has joined the network somewhere in the past but it does not mean that is presently associated.
Well, I can understand that, but still I think that it is not clearly remarked in Digi documentation.

I think there is some confusion. The Association indicator is as it is documented in the Zigbee and IEEE 802.15.4 standards. It is not the same as an IEEE 802.11 device where it tells you the exact status at that time. It can only tell you its status as of the last Joining event happened. That is why the Network Watchdog timer exists. It allows a Router to verify that it is still on a valid network with a Coordinator. It does that by looking for messages from the Coordinator being past through at least once every three times the NW period. If it is not received, then it performs a local network watchdog reset looking for the network to join.