Updating creates duplicate records in dynamodb

Question

I am using a docker image of dynamodb. Whenever i try to perform an update operation on the table, it creates a new record with the same primary key instead of updating the existing one. Once this is done, I can't delete the row or do anything on it. The only solution that is currently working is deleting the old record and creating a new one.

My table definition is:

{
    TableName: "commission",
    KeySchema: [
      { AttributeName: "public_key", KeyType: "HASH" }, //Partition key
    ],
    AttributeDefinitions: [{ AttributeName: "public_key", AttributeType: "S" }],
    ProvisionedThroughput: {
      ReadCapacityUnits: 5,
      WriteCapacityUnits: 5,
    },
  }

Update query generated using NoSQL Workbench:

{
        TableName: "commission",
        Key: {
            "public_key": publickey
        },
        UpdateExpression: "set commission = :commission , commisison_limit = :commissionlimit ",
        ExpressionAttributeValues: {
            ":commission": commission,
            ":commissionlimit": commissionlimit
        },
        ReturnValues: "UPDATED_NEW"

    }