DHCP / MAC / different LAN difficulties?

Is there any logical explanation for this?

I have set up a RB3011 as CAPSMAN, with three different SSID’s that points to three different bridges/VLAN’s. There is a DHCP server with separate pool on each bridge.
Everything works fine when connecting something to either of the SSID’s.
But when I connect a phone (android) to one of the SSID and then change directly to connect to one of the other I connect fine but can’t get an IP address.
If I wait for a while I eventually get assigned an IP address and everything works fine.
Is there a problem with connecting to another bridge with the same MAC for example? What can I do do prevent this? In the real world this shouldn’t be a problem, but for at least for testing purposes its a pain..