have a voWifi Project at the moment. One site about 180 APs with 2 C35 Controller in an Availability Pair and the other site 580 APs and C5215 controllers also in an Availability Pair.
The handsets are Open Stage WL3 phones. They are more or less the same as the Ascom i62.
It is a WPA-PSK environment.
Now the interesting fact, as log as i roam between APs homed at the same controller, everything works fine. When I roam between 2 APs on the opposite controller in the same Availability Pair, the handset can not see the next AP and it takes about 20 seconds to reconnect. The phonecall itself remains. So I can not hear anything but as far as i am reconnected the session still exists and the other can hear me without dialing again.
This Problem exists on both sites.
I did an experiment. I rehomed a few APs in a row to the other controller, and the problem moved "a few APs further"
Session remains, roaming does not work between APs on different controllers within the same Availabilty pair.