Let's get more details...
- is the EWC and the APs in the same VLAN/subnet
- is the problem new after upgrading to this release or is that a new installation
- how often does it happen
- are all APs affected at the same time
In general I'd turn on a port mirror of the EWC port and check the trace file.
If you filter on "wassp.type == 16" you should see a WASSP poll from the AP to the EWC and then the answer in the return direction.
But it depends, I had the same issue and checked the logs for one AP with the most reboot (my SSID was routed so the AP has done an reboot) and turned on a port mirror on the AP port do reduce the trace data size.
I've troubleshooted for weeks, tried everything, at the end I've replaced my C4110 and the problem was gone..... so sometimes it's try & error.