I think this is related to changes from rev. 2721
Ingame you see many "Invalid Position" messages now on the console also there is no reason to do this!
One example can be reproduced like this:
- start a game with you playing indian faction
- tell the three workers to buidl a second main tent
- now directly select the 3 building/repairing workers and tell them to build a third tent.
Becasue you have not enough resources the command is aborted, but you see two "Invalid Position" messages now.
As I say, this is only one example:
In a multiplayer game I saw many mesages like this on the ingame console, sometimes without commanding any of my units!
Maybe these console messages were somehow caused by the others players?