The recent update for Pokémon GO brought a few new codes hidden in the APK. Well, an anticheat fail code had been added.
This is, of course, to help limit the number of spoofers which there are still a few left that managed to get around the system. The purpose of this fail code has something to do either Pokemon encounters.
At first, Niantic had encounter blocked by where the Pokémon was caught. Making them flee after it was so far away. Recent finds suggested that Niantic had planned on trying to get it to work for where a trainer is and where the Pokémon was ecountered.