I guess it's related to MCPE-27720, but I figured out a work-around to unlock the achievement.
To recreate the issue you can place a few maps down in a room. I dont think the quantity matters, but place at least 5 of them down in frames as normal.
Then place down the 9 maps needed for the achievement. It should NOT unlock. Once you remove the 5 or so maps from before and then redo the 9 maps again, then the acheivement should unlock... it did for us.
I guess it's related to MCPE-27720, but I figured out a work-around to unlock the achievement.
To recreate the issue you can place a few maps down in a room. I dont think the quantity matters, but place at least 5 of them down in frames as normal.
Then place down the 9 maps needed for the achievement. It should NOT unlock. Once you remove the 5 or so maps from before and then redo the 9 maps again, then the acheivement should unlock... it did for us.