WLC 5508 in HA SSO mode, problems with failover

[tvelasco]

We have two 5508's in HA SSO mode connected via RP port. 
 

When on the secondary unit, all AP's are connected without any problems.  When we force failover back to the primary, 30+ ap's randomly fail to connect.  The AP's are pingable, and on the network.  They just don't establish the tunnel to the WLC.  Any ideas?

[Freerk Terpstra]

Did you make sure that all of the switchport configurations are the same? So all of the VLAN's are allowed for both WLC's? Also which software release are you currently running on those WLC's?