Two bridges, two devices sharing the same MAC but one on bridge1 and another on bridge2

Sure, and introduce by mistake 2 to 34 of the possible 4587 differences between your configuration and the recreated one.

Come on :slight_smile: , follow these instructions and post (anonymized) the EXACT configuration you are testing:
http://forum.mikrotik.com/t/forum-rules/173010/1
maybe this way someone will take the time to reproduce/test it.