Symptom:
This can be produced by following these steps

1.) make RAP port connected to uplink switch as trunk and using Native VLAN for AP-WLC communication (let say VLAN 100)
2.) Make the bridge port on AP as part of any other VLAN(let say 350)
3.) device attached to bridge port will get IP address from DHCP server from VLAN 350 scope and start working
4.) reboot or restart AP, this will make the bridge connected traffic to be send as untagged till AP join WLC. during this period device send a dhcp request again and due to untagged packet it will get IP address from VLAN 100 Range. once AP join WLC the bridge port start putting VLAN 350 tag on packet coming from device as per the configuration done in step 2.
5. Due to this now device is unreachable since it receive IP address from VLAN 100 and port is in VLAN 350.

Conditions:
Unreachable device if they have DHCP capable.