Code:
function impact_event()
{
  if(event_type == EVENT_IMPACT)
  {
    my.event = NULL;
    my.skill2 = 0;
  }
}

action colider()
{
  my.emask |= ENABLE_IMPACT;
  my.event = impact_event;
  set(my,POLYGON);
 
  my.skill2 = 1;
  while(my.skill2) { wait(1); }

  level_load("cave.wmb");
}


Do not load the level directly from the event function OR put a wait(1); before load the level. Maybe this does the trick.