Chunk size bigger than configured
To split you can use something like this... 

sh.stopBalancer();
var c=0;
db.chunks.find({ns:"database.collection", "shard" : "S0RS0"}).sort({$natural:1}).limit(1400).forEach(function(d)
{
  printjson(d.min);printjson(d.max);
  var tulos=db.adminCommand( { split: d.ns, bounds: [ d.min, d.max ] } );
  if (tulos.ok &lt; 1) {
    print("Split ERROR");
    printjson(tulos);
  }
  print(c);
  c++;
})
sh.startBalancer();