When you get

Client Excluded: MACAddress:2c:be:08:f5:14:d6 Base Radio MAC :2c:d0:2d:91:54:86 Slot: 1 User Name: unknown Ip Address: unknown Reason:Attempted to use IP Address assigned to another device. ReasonCode: 3

you can debug the already used ip by enable dhcp debuging og the wlc controller

you can enable debuging by using the following command

debug dhcp message enable

you can look for the event

*DHCP Socket Task: Oct 11 09:11:56.591: 2c:be:08:f5:14:d6 DHCP option: requested ip = 10.16.0.254

then you know that the ip that is already in use is 10.16.0.254, and you can exclude it on the dhcp server

Cisco wlc2504 lag with SG300

ssh to SG300

config t
interface range GigabitEthernet x-y
channel-group 1 mode on