At 3:12 a.m. on 23 April 1986, the alarm was activated at the barracks of the Suchohrad unit. The alarm on the wire barrier also triggered the light barrier. A series of floodlights installed on the wall marked the spot where an unknown person attempted to dig a hole under the barrier. Upon arrival of the alarm patrol, they only found a small hoe and a hole in the ground. The person returned inland after this unsuccessful attempt to cross the border. The identity of this person remains a mystery to this day.