Hello,
I've now had my case resolved.
I wanted to share the conclusion in case it's useful to anyone else.
In the end nothing to do with Ruckus- my issue was down to Apple's keychain.
It seems (possibly from iOS release 10?) that keychain shares WLAN passcodes via iCloud.
So, the issues I was seeing were among devices that shared iCloud accounts. Specifically I had 2 pairs of devices (in each case an iPhone and iPad) which were having connection issues.
Assuming unique Ruckus Pre-shared Keys (PSK), manually updating the WLAN PSK passcode on (for example) the iPad, resulted in that passcode being shared with the iPhone (via iCloud and keychain) which would promptly result in the iPhone failing authentication and disconnecting from the WLAN. The same was true the other way around,iPhone to iPad with the same mechanism.
So, I guess to generalize (and this may be obvious to most people, but certainly missed by me) iOS or MAC devices which share an iCloud account cannot use manually shared PSKs. Keychain will result in the latest PSK being exchanged among all devices which share the iCloud account.
The issue may not exist if Ruckus Profiles are used on Apple devices- but I wasn't able to test or verify that.
In the end I used a dedicated WLAN just for Apple devices.
Turning off Keychain would also work- although perhaps not desirable for most Apple users.
I hope this is useful.
Kind Regards,
Andy.