BulkProcessor .add() not finishing when number of bulks > concurrentRequests - amazon-web-services

Question

Here is a sample of the code flow:
Trigger the process with an API specifying bulkSize and totalRecords.
Use those parameters to acquire data from DB
Create a processor with the bulkSize.
Send both the data and processor into a method which:
-iterates over the resultset, assembles a JSON for each result, calls a method if the final JSON is not empty and adds that final JSON to the process using processor.add() method.
This is where the outcome of the code is split
After this, if the concurrentRequest parameter is 0 or 1 or any value < (totalRecords/bulkSize), the processor.add() line is where the code stalls and never continues to the next debug line.
However, when we increase the concurrentRequest parameter to a value > (totalRecords/bulkSize), the code is able to finish the .add() function and move onto the next line.
My reasoning leads me to believe we might be having issues with our BulkProcessListener which is making the .add() no close or finish like it is supposed to. I would really appreciate some more insight about this topic!
Here is the Listener we are using:
private class BulkProcessorListener implements Listener {
#Override
public void beforeBulk(long executionId, BulkRequest request) {
// Some log statements
}
#Override
public void afterBulk(long executionId, BulkRequest request, BulkResponse response) {
// More log statements
}
#Override
public void afterBulk(long executionId, BulkRequest request, Throwable failure) {
// Log statements
}
}
Here is the createProcessor():
public synchronized BulkProcessor createProcessor(int bulkActions) {
Builder builder = BulkProcessor.builder((request, bulkListener) -> {
long timeoutMin = 60L;
try {
request.timeout(TimeValue.timeValueMinutes(timeoutMin));
// Log statements
client.bulkAsync(request, RequestOptions.DEFAULT,new ResponseActionListener<BulkResponse>());
}catch(Exception ex) {
ex.printStackTrace();
}finally {
}
}, new BulkProcessorListener());
builder.setBulkActions(bulkActions);
builder.setBulkSize(new ByteSizeValue(buldSize, ByteSizeUnit.MB));
builder.setFlushInterval(TimeValue.timeValueSeconds(5));
builder.setConcurrentRequests(0);
builder.setBackoffPolicy(BackoffPolicy.noBackoff());
return builder.build();
}
Here is the method where we call processor.add():
#SuppressWarnings("deprecation")
private void addData(BulkProcessor processor, String indexName, JSONObject finalDataJSON, Map<String, String> previousUniqueObject) {
// Debug logs
processor.add(new IndexRequest(indexName, INDEX_TYPE,
previousUniqueObject.get(COMBINED_ID)).source(finalDataJSON.toString(), XContentType.JSON));
// Debug logs
}