None of these “incursions” are by mistake. The well funded drug cartels have GPS and other ways to place their agents, including the Mexican military, exactly where they want them. This is nothing more than protecting a drug/human trafficking business.
There is a fence (small barb-wire) on the border, as well as a plowed dirt road the agents drive looking for sign of traffic.
The Mexican military knows exactly where they are when it comes to the border.