I am looping through all artists in the db and issuing following three queries for each:

• Update img in artist by id
  db.artists.update( { _id: "sSKwjm_S1go" }

  ,

  Unknown macro: { $set}

  )

• Update all simarts.img for all artists
  db.artists.update( { simarts.id: "sSKwjm_S1go" }

  ,

  Unknown macro: { $set}

  )

• Update all tagart img by artistId
  update cl.tagarts query: { artistid: "sSKwjm_S1go" }

  update:

  Unknown macro: { $set}

  db.tagarts.update(

  { artistid: "sSKwjm_S1go" }

  ,

  Unknown macro: { $set}

  )
  THIS IS THE QUERY WHICH FAILS SOMETIMES

Get this exceptions in the log when i am updating, example log:

update cl.artists query:

{ _id: "sSKwjm_S1go" }

update: { $set:

{ img: "D1FD71F8B062F0C8" }

} 0ms
update cl.artists query:

{ simarts.id: "sSKwjm_S1go" }

update: { $set:

{ simarts.$.img: "D1FD71F8B062F0C8" }

} 31ms
Assertion: 13000:invalid keyNode:

{ "i" : 100, "n" : 100 }

Caught Assertion in update , continuing
update cl.tagarts query:

{ artistid: "sSKwjm_S1go" }

update: { $set:

{ image: "D1FD71F8B062F0C8" }

} exception massert:invalid keyNode:

{ "i" : 100, "n" : 100 }

15ms
update cl.artists query:

{ _id: "Nd4OdVNHflU" }

update: { $set:

{ img: "E2CD326B2E47EF56" }

} 0ms
update cl.artists query:

{ simarts.id: "Nd4OdVNHflU" }

update: { $set:

{ simarts.$.img: "E2CD326B2E47EF56" }

} 31ms
update cl.tagarts query:

{ artistid: "Nd4OdVNHflU" }

update: { $set:

{ image: "E2CD326B2E47EF56" }

} 0ms
update cl.artists query:

{ _id: "jeX7zu5fEYE" }

update: { $set:

{ img: "3F8264975F62116C" }

} 0ms
update cl.artists query:

{ simarts.id: "jeX7zu5fEYE" }

update: { $set:

{ simarts.$.img: "3F8264975F62116C" }

} 31ms
update cl.tagarts query:

{ artistid: "jeX7zu5fEYE" }

update: { $set:

{ image: "3F8264975F62116C" }

} 0ms
update cl.artists query:

{ _id: "JsSAZfOn7NA" }

update: { $set:

{ img: "61EE3041543A7F18" }

} 0ms
update cl.artists query:

{ simarts.id: "JsSAZfOn7NA" }

update: { $set:

{ simarts.$.img: "61EE3041543A7F18" }

} 15ms
Assertion: 13000:invalid keyNode:

{ "i" : 96, "n" : 96 }

Caught Assertion in update , continuing
update cl.tagarts query:

{ artistid: "JsSAZfOn7NA" }

update: { $set:

{ image: "61EE3041543A7F18" }

} exception massert:invalid keyNode:

{ "i" : 96, "n" : 96 }

0ms
update cl.artists query:

{ _id: "fcdNwrJjCLw" }

update: { $set:

{ img: "2E68C6FF30CCD6B9" }

} 0ms
update cl.artists query:

{ simarts.id: "fcdNwrJjCLw" }

update: { $set:

{ simarts.$.img: "2E68C6FF30CCD6B9" }

} 31ms
Assertion: 13000:invalid keyNode:

{ "i" : 100, "n" : 100 }

Caught Assertion in update , continuing
update cl.tagarts query:

{ artistid: "fcdNwrJjCLw" }

update: { $set:

{ image: "2E68C6FF30CCD6B9" }

} exception massert:invalid keyNode:

{ "i" : 100, "n" : 100 }

0ms