Hi Sudhakar,
Yes. You should try and split them manually using splitAt.
The other issue is that these chunks may only contain documents for a single given value in your shard key.
Ie the chunk { "clientId" : NumberLong(38) } -->> { "clientId" : NumberLong(51) } may only have documents with clientId of 38 and as such would not be able to be split.
Regards,
David