AWS Lambda finished before return call or a timeout

I have only seen this one time, but want to understand the reason behind it.

I have a AWS lambda function written in nodeJS that just add vertex to AWS neptune.

Here is the relevant code

async function updateDoc (dataTmp, callback, logData, errorData) {
  try {
    console.log('inside updateDoc function')
    console.log('dc', dc)
    console.log('g', g)
    var userAdded = await g.addV('user').property('userId', dataTmp.userId).property('firstName', dataTmp.firstName).next()
    console.log('userAdded', userAdded)
    return callback(null)
  } catch (e) {
    console.log('error', e)        
    return callback(null)
  }
}

Timeout set for this function is 20 seconds. Most of the time this functions just works fine and return in 11 to 50 ms.

This one time, I saw function just stopped execution after printing third console.log statement. Initially, I thought, lambda might be waiting for Neptune to return (await statement), but in that case lambda should timeout and retry again.

Here is the output from cloudwatch

Notice that after last console.log, execution ends

INFO    g GraphTraversalSource { [+5ms]
  graph: Graph {},
  traversalStrategies: TraversalStrategies { strategies: [ [RemoteStrategy] ] },
  bytecode: Bytecode { sourceInstructions: [], stepInstructions: [] },
  graphTraversalSourceClass: [Function: GraphTraversalSource],
  graphTraversalClass: [Function: GraphTraversal]
}
REPORT  Duration: 42.51 ms  Billed Duration: 100 ms Memory Size: 1024 MB    Max Memory Used: 103 MB  [+46ms]

Usual output of the lambda looks like this

g GraphTraversalSource { [+4ms]
  graph: Graph {},
  traversalStrategies: TraversalStrategies { strategies: [ [RemoteStrategy] ] },
  bytecode: Bytecode { sourceInstructions: [], stepInstructions: [] },
  graphTraversalSourceClass: [Function: GraphTraversalSource],
  graphTraversalClass: [Function: GraphTraversal]
}
2 hours ago INFO    userAdded { [+46ms]
  value: Vertex {
    id: '9cb979cb-427e-97d2-f265-fee7b8b94780',
    label: 'user',
    properties: undefined
  },
  done: false
}
REPORT  Duration: 43.74 ms  Billed Duration: 100 ms Memory Size: 1024 MB    Max Memory Used: 103 MB  [+47ms]

Any thoughts on what might be happening here and why this lambda is returning before the timeout.

Thanks