diff --git a/pos_android_studio_demo/pos_android_app/build.gradle b/pos_android_studio_demo/pos_android_app/build.gradle
index 6f871e1d..b2b48d47 100644
--- a/pos_android_studio_demo/pos_android_app/build.gradle
+++ b/pos_android_studio_demo/pos_android_app/build.gradle
@@ -32,7 +32,7 @@ android {
         minSdk 24
         targetSdk 34
         versionCode 146
-        versionName "8.5.4-2608201515"
+        versionName "8.5.4-2609021540"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         ndk {
             // Set up supported SO library architecture
@@ -41,6 +41,9 @@ android {
     }
 
     buildTypes {
+        debug {
+          debuggable false
+        }
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
diff --git a/pos_android_studio_demo/pos_android_app/src/main/java/com/dspread/pos/ui/setting/connection_settings/ConnectionSettingsFragment.java b/pos_android_studio_demo/pos_android_app/src/main/java/com/dspread/pos/ui/setting/connection_settings/ConnectionSettingsFragment.java
index 97ec20c5..9ac84b27 100644
--- a/pos_android_studio_demo/pos_android_app/src/main/java/com/dspread/pos/ui/setting/connection_settings/ConnectionSettingsFragment.java
+++ b/pos_android_studio_demo/pos_android_app/src/main/java/com/dspread/pos/ui/setting/connection_settings/ConnectionSettingsFragment.java
@@ -212,8 +212,26 @@ public String getTitle() {
     }
 
 
-    // Thread pool for executing asynchronous operations
-    private static final java.util.concurrent.ExecutorService asyncExecutor = java.util.concurrent.Executors.newSingleThreadExecutor();
+    // Thread pool for executing asynchronous operations.
+    // Instance-level (not static): a static pool would be permanently terminated by the first
+    // fragment's onDestroy, causing RejectedExecutionException for later instances.
+    private final java.util.concurrent.ExecutorService asyncExecutor = java.util.concurrent.Executors.newSingleThreadExecutor();
+
+    /**
+     * Safely submit a task to the executor, guarding against a terminated pool
+     * (e.g. USB permission callback fired after the fragment was destroyed).
+     */
+    private void executeAsync(Runnable task) {
+        if (asyncExecutor.isShutdown() || asyncExecutor.isTerminated()) {
+            TRACE.d("asyncExecutor already terminated, skip task submission");
+            return;
+        }
+        try {
+            asyncExecutor.execute(task);
+        } catch (java.util.concurrent.RejectedExecutionException e) {
+            Log.e("ConnectionSettingsFragment", "submit task to executor failed: " + e.getMessage());
+        }
+    }
 
     private void showUsbDeviceDialog() {
         USBClass usb = new USBClass();
@@ -221,7 +239,7 @@ private void showUsbDeviceDialog() {
             @Override
             public void onPermissionGranted(UsbDevice device) {
                 // Get USB device list in sub-thread
-                asyncExecutor.execute(() -> {
+                executeAsync(() -> {
                     ArrayList<String> deviceList = usb.GetUSBDevices(getActivity());
                     // Update UI in main thread, using main thread's Looper
                     new Handler(Looper.getMainLooper()).post(() -> {
@@ -239,7 +257,7 @@ public void onPermissionDenied(UsbDevice device) {
         });
 
         // Get USB device list in sub-thread
-        asyncExecutor.execute(() -> {
+        executeAsync(() -> {
             ArrayList<String> deviceList = usb.GetUSBDevices(getActivity());
             // Update UI in main thread, using main thread's Looper
             new Handler(Looper.getMainLooper()).post(() -> {