That happened first with me on the last beta of the 6.48 map.
The menu switches by itself. When you click the menu to build, it displays the walls, and towers, but when you click on the wall( it's on the same spot where the lumber mill stays ) some times the lumber mill is picked, others it's the wall.
It's really strange. The menu changes by itself, you dont need to switch it back.
Example: You press the hotkey to build, and then it shows the second menu( walls and towers ). You can cancel, and then click on the hotkey again( without switching menus ) and it will display the first menu. That doesn't mean that it will change back that easy.
If you click on the switch button, it will keep coming back and forward.
The final version of the map also have this bug.
Another one is the heroes bug.
When a player leaves the game, his units used to die, and the buildings be ceded to the closest player on the game.
Now, that still happens, but the units don't die anymore, so when someone leaves, other players get their heroes.
Another one is that, playing a game yesterday, some invisible units, just appeared inside the base, with the walls intact.
I don't know how it happened, since i wasn't looking in the moment, but i can assume it's definitely not normal.