Flutter stack overflow error on using python script

I was trying to integrate a basic network scanner using python into flutter. The scanner function returns a List in the format List[List, Int]. To call this I use MainActivity.kt like this

package com.example.ctos

import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel
import com.chaquo.python.Python
import com.chaquo.python.android.AndroidPlatform

class MainActivity: FlutterActivity() {
    private val CHANNEL = "python"

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        
        // Initialize Python
        if (!Python.isStarted()) {
            Python.start(AndroidPlatform(this))
        }
        
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
            when (call.method) {
                "startScan" -> {
                    val hosts = call.argument<String>("hosts")
                    val ports = call.argument<String>("ports")
                    val scanType = call.argument<String>("scanType")
                    
                    val py = Python.getInstance()
                    val results = py.getModule("network_scanner")
                        .callAttr("startScan", hosts, ports, scanType)
                    
                    result.success(results)
                }
                else -> result.notImplemented()
            }
        }
    }
}

And a python bridge to call the script

import 'package:flutter/services.dart';

class PythonBridge {
  static const MethodChannel _channel = MethodChannel('python');

  static Future<List> scanPort(
      String hosts, String ports, String scanType) async {
    return await _channel.invokeMethod(
        'startScan', {'hosts': hosts, 'ports': ports, "ScanType": scanType});
  }
}

and in the dart fileusing a try catch I am calling it like this

 var results = await _channel.invokeMethod('startScan', {
        'hosts': '192.168.84.229',
        'ports': '8999-9001',
        'scanType': 'tcp_scan'
      });

      print(results);

The python script have print statements to make sure its working and whenever the function is called through dart I can see the output is getting printed after all scan is done. Scans are done through threads for parallel processing.

with ThreadPoolExecutor(max_workers=max_threads) as executor:
        future_to_target = {
            executor.submit(tcp_single_scan, host, port, timeout): (host, port) for host, port in scan_targets
        }
        
        for future in as_completed(future_to_target):
            result = future.result()
            results.append(result)
            completed+=1
            progress = (completed / total) * 100
            if(int(progress) != int_progress):
                print(str(int(progress))+"%")
                int_progress = int(progress)

But after all scan done I am getting stack overflow error and app gets exit.

Is this something related to threads. I even tried with just scanning one port and still causing issue.