"A stall is already present"

[DaFigPig]

I've seen this message a few times in game and it seems to let the player draw a new tile. It's only happened to opponents thus far and despite me looking over the rules and the tutorial I can't seem to find anything about it. It doesn't seem broken or anything I would just like to know the context for this as my understanding is that you can have more than two of any stall type. I may have just missed it in the rules but thanks in advance if anyone knows the answer.

[Shaz the Cat]

You get this msg when you already have the same tile (only on a connected path) Then you are awarded an extra tile from the supply (not the board). You can do this multiple times for each stall. Any player can place a duplicated stall