Mongodb shard balancing failed
As I am able to see the chunks error such as 


  3826 : Failed with error 'moveChunk failed to engage TO-shard in the
  data transfer: can't accept new chunks because there are still 7
  deletes from previous migration', from shard0000 to shard0001 7655 :
  Failed with error 'moveChunk failed to engage TO-shard in the data
  transfer: can't accept new chunks because there are still 4 deletes
  from previous migration', from shard0001 to shard0000


As Asya Kamsky google groups documentation here When importing a large amount of data it is always preferable to pre-split the collection and distribute chunks evenly across the shards and disable balancer  before starting the data load.   Otherwise you will see the migrations and new data load compete for the same resources, reducing the performance of both.

Yes, you should/can re-enable the balancer after the import is done.   But of course it's better to presplit/pre-balance as described  here.

For further your ref here