I am trying to mongorestore a dump (created by v2.6 mongodump) to v3.2 mongod and getting a lot of "E11000 duplicate key error". However, after the restore, the new collection seems to have all records.
The same dump works fine without error when restored to a v2.6 mongod.
The fact that it is a dump created by mongodump and it works without error when restored to a 2.6 mongod confirms that there are no duplicate records in the dump. Wondering if these are false errors

2016-03-01T00:56:47.260+0000 error: multiple errors in bulk operation:

• E11000 duplicate key error collection: Reports.RestoredCollection index: id dup key: { : { T: new Date(1456358400000), AD: 130318, PB: 10264, CG: 307 }

  }

btw, I tried option --drop too just in case but didn't help as expected.