Unable to fetch private data from collection. Getting blank response - node.js

Question

I am trying to explore private data collection and I have written the chaincode in javascript. I am passing the proper collections file while instantiating the chaincode and while invoking the chaincode I am adding the transient data in request payload which looks like this :
const proposal_request = {
chaincodeId: chaincodeId,
fcn: functionName,
args: args,
chainId: channelCode,
txId: tx_id,
transientMap : { "private" : "test data"}
};
My chaincode file looks like this :
const shim = require('fabric-shim');
const util = require('util');
var PrivateDataChaincode = class {
// Initialize the chaincode
async Init(stub) {
console.log('<================> ::Private Data Chaincode Instantion:: <=================>');
return shim.success();
}
async Invoke(stub) {
console.log('<================> ::Private Data Chaincode Invocation:: <=================>');
let ret = stub.getFunctionAndParameters();
console.info(ret);
let method = this[ret.fcn];
console.info('methodName');
console.info(method);
if (!method) {
console.error('No method of name:' + ret.fcn + ' found');
return shim.error('No method of name:' + ret.fcn + ' found. \n UNKNOWN FUNCTION INVOCATION: ' + ret.fcn);
}
console.info('\nCalling method : ' + ret.fcn);
try {
let payload = await method(stub, ret.params);
return shim.success(payload);
} catch (err) {
console.log(err);
return shim.error(err);
}
}
async createPrivateDataInCollection(stub, args) {
if (args.length != 2) {
throw new Error('Incorrect number of arguments. Expecting 2');
}
// arg[0] has the collection name
// arg[1] has the key
console.info("============= START : Create Private data ===========");
// get the transient map
let transientData = stub.getTransient();
await stub.putPrivateData(args[0], args[1], transientData.map.private.value);
console.info('============= END : Create private data ===========');
}
async queryPrivateDataInCollection(stub, args) {
console.info('============= START : Query private Data ===========');
// arg[0] has the collection name
// arg[1] has the key
// query private data with argument
let allResults = await stub.getPrivateData(args[0], args[1]);
if (!allResults) {
throw shim.error("Can't get data from state");
}
console.log(allResults);
return allResults;
}
};
shim.start(new PrivateDataChaincode());
I am storing data using the createPrivateDataInCollection method and fetching the data using queryPrivateDataInCollection. The private data is getting stored correctly when I cross checked in the couch DB. The problem I am facing is that I am getting a blank response when I am querying the private data using queryPrivateDataInCollection method on some occasions. Sometimes I am able to see the data, while sometimes I am getting a blank response. Am I missing something important?