I tried the 5 seconds delay in my driver, but unfortunately, it didn't help...
The PCAP file below is sniffed when _TZ3000_okaz9tjs pairs to HE using the Generic Zigbee Outlet driver.
The device changed the NWK several times:
20:59:43.00 Device Announcement (zbee_nwk.addr eq 0xc4b0)
20:59:44.29 leave
29:59:50.67 Device Announcement (zbee_nwk.addr eq 0x78b4)
20:59:51.58 leave
20:59:56.68 Device Announcement (zbee_nwk.addr eq 0x3a95)
20":59:57.18 leave .....
...
The Zigbee logs show multiple devices during the pairing process ('device', 'b')
https://drive.google.com/file/d/1TiP5BvtBzbE7y5a_q5-NS1BCDHkGFrZp/view?usp=sharing
Don't have an idea why this problem doesn't show up in your environment...
Here are links to other HE users reporting the same problem: link1 link2 link3 link4 link 5 link6 link7
Hope this helps.