MT knows about issues for sure, like here with vlan mtu: http://forum.mikrotik.com/t/v7-14rc-testing-is-released/173569/146
It is also the acknowledging reply from support when they can reproduce an issue: “We are aware of this issue, and we look forward to fixing it on an upcoming RouterOS versions.”
So MT does have an internal list of known issues. But they are kept top secret.