MAC flapping reported between 2 port channels on Nexus 5596

Hi all, I'm seeing messages like the following reported on a Nexus 5596:

2015 Jan 7 12:40:48.954 Switch-5596A %FWM-6-MAC_MOVE_NOTIFICATION: Host 00ab.cdef.0123 in vlan 104 is flapping between port Po5 and port Po10

Po5 is connected to a storage cluster and is configured as an access port:

interface port-channel5 description Storage Shelf 1 priority-flow-control mode off switchport access vlan 104 spanning-tree port type edge spanning-tree bpduguard enable speed 10000 flowcontrol receive on vpc 5

Po10 is the uplink to the core switch:

interface port-channel10 description uplink switchport mode trunk switchport trunk native vlan 2702 switchport trunk allowed vlan 64,94,104,124 spanning-tree port type network speed 10000 vpc 10

Any ideas on why we would be seeing these log messages?

Thank you.