Greetings, First off, I'm well aware that the ZD1000 is EoL - I really just want to see if anyone else is or has experienced these issues, or may have some suggestions. That said, I have observed an interesting pattern with the combination of a ZD1000 with 7962 APs all running 220.127.116.11.21.
First off, certain devices intermittently won't see or be able to connect to any SSIDs being broadcast by 7962 APs with this firmware version. WPA and other settings don't seem to matter, and it only affects random devices (Nexus 5s, Samsung Notes, Nest thermostats, Roku media players so far), and only when broadcast on a 7962 AP - the same ZD configuration on a 7363 or 2942 work fine every time with the above listed devices.
The second issue I've noted is the Automatic 1/6/11 Channel Selection seems to be ignored on all AP models with this firmware. Each AP Group is configured to "Auto" Channel Selection between 1,6,11 per the GUI, and I have attempted setting it via CLI as well - the setting appears set in both instances, but APs are frequently seen on any of the twelve channels.
Finally, I set up a spare ZD1000 in our lab, factory defaulted it, upgraded to 18.104.22.168.21 from some older version, added a few APs and each of the above scenarios are repeatable, so I don't think it's anything in my config in the 'in production' device'.
ChannelFly is available in 9.3 for ZD1000s too. Check you AP Group, where you may have excluded channels other than 1/6/11. CF looks at non 802.11 RF interference, that Background Scanning alone does not, but with the channel selection options, you can restrict CF to use only the same 1/6/11 (although using all 1-11 should provide 30% better capacity).