There are multiple different reasons for APs system fault reboots. We have to check the AP support info file for more details.
Also, we have to enable himem logs to get the debug level details about the crash/reboot.
Unknown reboots generally occur if there is any power issue. Again, for this issue also, we need the complete support info file of the AP to know the root cause.
I would recommend to open a case with Ruckus Support to further analyse the reboots and fix them.