diff --git a/CHANGELOG.md b/CHANGELOG.md
index 24f8292..8905669 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 	OpenSeizureDetector Android App - Change Log
 	============================================
 
+    V4.2.4 - Added checks and a FAULT condition for Bluetooth errors in Bluetooth Data Source
     V4.2.3 - Uses 3d accelerometer data to calculate magnitude if vector magnitude is not sent from data source.
            - fixed latched alarms (Issue #146)
            - fixed HR alarms selection issue (#153)
diff --git a/app/release/app-release-4.2.3.apk b/app/release/app-release-4.2.4.apk
similarity index 84%
rename from app/release/app-release-4.2.3.apk
rename to app/release/app-release-4.2.4.apk
index 12820d5..c7e8299 100644
Binary files a/app/release/app-release-4.2.3.apk and b/app/release/app-release-4.2.4.apk differ
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 8d42d03..f38b9e6 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -2,7 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:versionCode="138"
-    android:versionName="4.2.4b">
+    android:versionName="4.2.4">
     <!-- android:allowBackup="false" -->
     <uses-permission android:name="android.permission.BLUETOOTH" />
     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
diff --git a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
index 61c61c0..4c07aa7 100644
--- a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
+++ b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
@@ -368,21 +368,31 @@ public class SdDataSourceBLE extends SdDataSource {
          * @param gattCharacteristic - the characteristic to be read.
          */
         private void executeReadCharacteristic(BluetoothGattCharacteristic gattCharacteristic) {
-            if (gattCharacteristic != null) {
-                boolean retVal = mBluetoothGatt.readCharacteristic(gattCharacteristic);
-                if (retVal) {
-                    Log.d(TAG, "executeReadCharacteristic - read initiated successfully");
-                } else {
-                    Log.d(TAG, "executeReadCharacteristic - read initiation failed - waiting, then re-trying");
-                    mHandler.postDelayed(new Runnable() {
-                        public void run() {
-                            Log.w(TAG, "Executing delayed read of characteristic");
-                            executeReadCharacteristic(gattCharacteristic);
-                        }
-                    }, 100);
-                }
+            if (gattCharacteristic == null) {
+                Log.i(TAG, "ExecuteReadCharacteristic() - gatCharacteristic is null, so not doing anything");
+                mUtil.showToast("ERROR: gatCharacteristic is null - this should not happen");
+                mSdDataReceiver.onSdDataFault(mSdData);
+                return;
+            }
+            if (mBluetoothGatt == null) {
+                Log.e(TAG, "executeReadCharacteristic() - mBluetoothGatt is null - Characteristic=" + gattCharacteristic.getUuid().toString());
+                mUtil.showToast("ERROR: mGatCharacteristic is null - this should not happen");
+                mSdDataReceiver.onSdDataFault(mSdData);
+                return;
+            }
+
+            // To get here both gatCharacteristic and mBluetoothGatt must be non-null
+            boolean retVal = mBluetoothGatt.readCharacteristic(gattCharacteristic);
+            if (retVal) {
+                Log.d(TAG, "executeReadCharacteristic - read initiated successfully");
             } else {
-                Log.i(TAG,"ExecuteReadCharacteristic() - gatCharacteristic is null, so not doing anything");
+                Log.d(TAG, "executeReadCharacteristic - read initiation failed - waiting, then re-trying");
+                mHandler.postDelayed(new Runnable() {
+                    public void run() {
+                        Log.w(TAG, "Executing delayed read of characteristic");
+                        executeReadCharacteristic(gattCharacteristic);
+                    }
+                }, 100);
             }
         }
 
@@ -391,27 +401,38 @@ public class SdDataSourceBLE extends SdDataSource {
          * of a given characteristic.
          * Because only one BLE operation can be taking place at a time, it may fail, in which case
          * the read is re-tried after a 100ms delay.
+         *
          * @param gattCharacteristic - the characteristic to be read.
-         * @param valBytes[] - array of bytes to send
-         * @param nBytes - number of bytes to send.
+         * @param valBytes[]         - array of bytes to send
+         * @param nBytes             - number of bytes to send.
          */
         private void executeWriteCharacteristic(BluetoothGattCharacteristic gattCharacteristic, byte[] valBytes) {
-            if (gattCharacteristic != null) {
-                gattCharacteristic.setValue(valBytes);
-                boolean retVal = mBluetoothGatt.writeCharacteristic(gattCharacteristic);
-                if (retVal) {
-                    Log.d(TAG, "executeWriteCharacteristic - write initiated successfully");
-                } else {
-                    Log.d(TAG, "executeWriteCharacteristic - write initiation failed - waiting, then re-trying");
-                    mHandler.postDelayed(new Runnable() {
-                        public void run() {
-                            Log.w(TAG, "Executing delayed write of characteristic");
-                            executeWriteCharacteristic(gattCharacteristic, valBytes);
-                        }
-                    }, 100);
-                }
+            if (gattCharacteristic == null) {
+                Log.i(TAG, "ExecuteWriteCharacteristic() - gatCharacteristic is null, so not doing anything");
+                mUtil.showToast("ERROR: gatCharacteristic is null - this should not happen");
+                mSdDataReceiver.onSdDataFault(mSdData);
+                return;
+            }
+            if (mBluetoothGatt == null) {
+                Log.e(TAG, "executeWriteCharacteristic() - mBluetoothGatt is null - Characteristic=" + gattCharacteristic.getUuid().toString());
+                mUtil.showToast("ERROR: mGatCharacteristic is null - this should not happen");
+                mSdDataReceiver.onSdDataFault(mSdData);
+                return;
+            }
+
+            // To get here both gatCharacteristic and mBluetoothGatt must be non-null
+            gattCharacteristic.setValue(valBytes);
+            boolean retVal = mBluetoothGatt.writeCharacteristic(gattCharacteristic);
+            if (retVal) {
+                Log.d(TAG, "executeWriteCharacteristic - write initiated successfully");
             } else {
-                Log.i(TAG,"ExecuteWriteCharacteristic() - gatCharacteristic is null, so not doing anything");
+                Log.d(TAG, "executeWriteCharacteristic - write initiation failed - waiting, then re-trying");
+                mHandler.postDelayed(new Runnable() {
+                    public void run() {
+                        Log.w(TAG, "Executing delayed write of characteristic");
+                        executeWriteCharacteristic(gattCharacteristic, valBytes);
+                    }
+                }, 100);
             }
         }
 
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index d41503d..23b3930 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -2,8 +2,9 @@
 <resources>
     <string name="app_name">OpenSeizureDetector</string>
     <string name="changelog">
-        "\n
-        \nV4.2.1 - Added support for PineTime Watches using Bluetooth data source.
+        "\nV4.2.4 - Fault alarm rather than crash if bluetooth system crashes.
+        \nV4.2.3 - Bug Fixes (heart rate alarm and latched alarm issues)
+        \nV4.2   - Added support for PineTime Watches using Bluetooth data source.
         \n       - Added new, swipeable user interface to simplify the main screen..
           "</string>
     <string name="UpgradeMsg">