Man

As I already explained to you the mines have a fixed deviation-range. If you do the deviation from the model itself it will NEVER be hit......
And since you need a LD test he can run over the mine without triggering it and one of the following mods triggers it then maybe they all stand inside the active radius of the mines.
And second it is all a bit relativated if you hold in mind that (afaik) you do the check at the end of the models action if it got through the 3 inch radius. so another possibility to get it nearer if the model only moves on a tangential if the radius.
And third for an angle of at least 90° the mine deviates in direction of the model the triggered it. Thats a 25% chance. Not so bad.....
Last but not least you have not only that on mine. There are other types of mines which will nearly everytime hit at least the triggering mod with keeping the chance of doing a lot more damage to the following group.