In my case, upgrading causes the IPSec policies to disappear. There are not visable in WinBox. Running /ip/ipsec/policy/print also produces nothing. Downgrading back to stable magically brings them back.
Also my wifi slave interface was stuck in a loop (Running flag flashing) Saw a glimpse of the red error displayed above the interface in Winbox, regarding Reselect Interwal. Had to unset it in the channel configuration, and reapply the setting one more time. After that we can see the message:
But now it has a permament "R" flag and it's working fine.