What we're seeing is that the ARP table of the core and distribution switches will display our gateway address, with the MAC of a seemingly random AP. Initially we thought it was just the VC, but now it appears that any AP will become the gateway.
10.190.78.1 is our gateway and 00005e-000101 is the core
Heres what it should look like when its working normally:
IP ARP table
IP Address MAC Address Type Port
--------------- ----------------- ------- ----
10.190.66.25 005056-9c1847 dynamic F1
10.190.66.86 98be94-29e1bb dynamic F1
10.190.66.93 005056-9c1791 dynamic F1
10.190.66.140 98fa9b-825ab3 dynamic D20
10.190.78.1 00005e-000101 dynamic F1
Here's what we get when it fails:
IP Address MAC Address Type Port
--------------- ----------------- ------- ----
10.190.66.25 005056-9c1847 dynamic F1
10.190.66.86 98be94-29e1bb dynamic F1
10.190.66.93 005056-9c1791 dynamic F1
10.190.66.140 98fa9b-825ab3 dynamic D20
10.190.78.1 20a6cd-ca2330 dynamic F1
or
IP Address MAC Address Type Port
--------------- ----------------- ------- ----
10.190.66.25 005056-9c1847 dynamic F1
10.190.66.86 98be94-29e1bb dynamic F1
10.190.66.93 005056-9c1791 dynamic F1
10.190.66.140 98fa9b-825ab3 dynamic D20
10.190.78.1 c8b5ad-c33a30 dynamic F1
So if we then track down which AP that is - and disable it, we start geting the correct response when pinging the gateway, the arp table will update with the core MAC