Mikael,
Is the Mobility Access Switch the DHCP server for your environment? If so, you're hitting a bug where we would send out option 43 with our own IP even though you did not configure it as such. It has been resolved in AOS 7.3 or higher images. If you can't upgrade, modify the DHCP scope to explicitly handout the IP address of the controller via option 43.
Best regards,
Madani