Have you configured smart roam and still the issue persist. If not can you please go through below and if in case you have an active Ruckus case kindly share the same to look at the progress and debug done so far.
We will need to dig a bit on the AP positioning and neighbor overlap for this issue. The smart roam is to define RSSI threshold below which AP will send disassociate to the client and look for better one. Kindly log a case with us if not and share the AP support log and client MAC in issue or you can share your availability for the TAC engineer to work further. We can test the roaming between two AP's at first and enable additional debug and capture on both of them to better understand the failure reason.