It is what it is... Your client connected to another AP...disconnected, registered to other interface
Access list is just a way to improve the Roaming, it is something like a workaround..nothing more nothing less...And don't tell me about fucking ACL or something.... It does'nt work.
Mikrotik does not support yet 802.11k or 802.11r protocols that provide a better roaming... 'k' works with neighbor list reports available to the Client and 'r' provides a seamless roaming, really great for voice applications, and what it actually does is the client authenticates it self to other APs(before the roam process) so when it is time to roam it has been already authenticated thus we have an ultra fast transition to the next AP...And don't fucking tell me about "roaming is completely controlled by the clients"...
But... This does not change the Fact that the client makes the decisions... Either if we talk about 802.11r or 802.11k or simple roaming...