Restarting a FAILED job is not processing the failed chunk data again : Continuation

Question

This is continuation for Restarting a FAILED job is not processing the failed chunk data again.

This is my step definition for spring batch partition approach,

@Bean public Step step1() { return new StepBuilder("step1", jobRepository) .partitioner(slaveStep().getName(), partitioner()) .step(slaveStep()) .gridSize(febpEmployeeTaxCalculationBatchProperties.getTaxCalculationStep1PartitionGridSize()) .taskExecutor(actStmntTaskExecutor()) .build(); }

    // slave step
    @Bean
    public Step slaveStep() 
    {
        
        try {
            return new StepBuilder("slaveStep", jobRepository)
                    .<EmployeeDetail, EmployeeTaxDetail>chunk(febpEmployeeTaxCalculationBatchProperties.getTaxCalculationStep1ReaderPageSize(),transactionManager)
                    .reader(pagingItemReader(null,null))
                    .processor(processor())
                    .writer(customerItemWriter())
                .taskExecutor(actStmntTaskExecutor())
                    .build();
        } catch (Exception ex) {
            throw new RuntimeException("Error creating slave step: " + ex.getMessage());
        }
    }
 /**
   * Act stmnt task executor.
   *
   * @return the simple async task executor
   */
  public SimpleAsyncTaskExecutor actStmntTaskExecutor() {
    SimpleAsyncTaskExecutor acctStmtTaskExecuter = new SimpleAsyncTaskExecutor();
    acctStmtTaskExecuter.setConcurrencyLimit(febpEmployeeTaxCalculationBatchProperties.getTaxCalculationStep1TaskExecuterThreadConcurrencyLimit());
    acctStmtTaskExecuter.setThreadPriority(febpEmployeeTaxCalculationBatchProperties.getTaxCalculationStep1TaskExecuterThreadPriority());
    acctStmtTaskExecuter.setThreadNamePrefix("FEBP_TAX_CALCULATION_GEN");
    return acctStmtTaskExecuter;
  }

So here,

1)Recommendation for restart is not using TaskExecuter. So should we not use TaskExecuter as mentioned above in step1() and slaveStep()?

2)What should be the chunk size with respect to gridSize or readers pagesize and fetchsize.? As I see if chunk size is set to low values, restart is not re-writting failed data.