You need to input more information ;
1. what model of WLC? ( Version of code)
2. what is the AP model?
3. what kind of authentication?
4. where is DHCP hand over take place
5. how different working vs not working ( same AP ?)
6. what frequency they connected 2.4 or 5 ( when you observe working, which one connected)
7. end device has the same chipset?