React Native Android - "Could not get BatchedBridge, make sure your bundle is packaged properly" - react-native

Question

Running on Android - I can no longer get my app to build. I've tried 15+ ideas on stack overflow with similar batchedbridge errors'.
Results - after packaging:
- Red error screen popups up with "Could not get BatchedBridge, make sure your bundle is packaged properly” (with no other callstack details) and then a second later get a blank white screen.
Results - after the error and then reloading from the app dev tools menu:
- Could not connect to development server
react-native version 0.40.0 npm=5.0.3 node=v7.4.0
The app was working previously for months so i'm guessing connected to a recent change, version problem, cache problem, npm version or reactnative version?
Tried adb reverse tcp:8081 tcp:8081
Tried npm cache clean
Tried on emulator and device - same issue
Tried closing all react packagers
Made sure no other react native apps/packagers running
Android app is building OK in Android Studio (without react native)
Looking in the logcat I seem some red flags but not sure if these problems are new or were previously there:
- Lots of 'ViewManagerPropertyUpdater: Could not find generated setter for class com.facebook.react.views.art.???????' etc
- React: The packager does not seem to be running as we got an IOException requesting its status: Connection reset
Here's the logcat snippet and stack trace from the app when it tries to start - if you need more of the logcat let me know (my attempt to add it here didn't work).
iceapp.challengeme ic=null D/FA: Connected to remote service W/unknown:ViewManagerPropertyUpdater: Could not find generated setter for class com.facebook.reactnative.androidsdk.FBLoginButtonManager V/FA: Processing queued up service tasks: 2 W/unknown:ViewManagerPropertyUpdater: Could not find generated setter for class com.facebook.reactnative.androidsdk.FBSendButtonManager W/art: Before Android 4.1, method boolean com.facebook.share.widget.ShareButtonBase.canShare() would have incorrectly overridden the package-private method in android.widget.TextView W/unknown:ViewManagerPropertyUpdater: Could not find generated setter for class com.facebook.reactnative.androidsdk.FBShareButtonManager
E/unknown:React: Exception in native call from JS
com.facebook.react.devsupport.JSException: Could not get BatchedBridge, make sure your bundle is packaged correctly
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31)
at android.os.Looper.loop(Looper.java:154)
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196)
at java.lang.Thread.run(Thread.java:762)
Caused by: com.facebook.jni.CppException: Could not get BatchedBridge, make sure your bundle is packaged correctly
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31) 
at android.os.Looper.loop(Looper.java:154) 
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196) 
at java.lang.Thread.run(Thread.java:762)  W/unknown:React: Packager connection already open, nooping. W/unknown:React: Inspector connection already open, nooping. E/unknown:React: Exception in native call
java.lang.RuntimeException: Error calling function: RCTDeviceEventEmitter:emit
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31)
at android.os.Looper.loop(Looper.java:154)
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196)
at java.lang.Thread.run(Thread.java:762)
Caused by: java.lang.RuntimeException: Empty Optional cannot be unwrapped
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31) 
at android.os.Looper.loop(Looper.java:154) 
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196) 
at java.lang.Thread.run(Thread.java:762)  E/unknown:React: Exception in native call
java.lang.RuntimeException: Error calling function: AppRegistry:runApplication
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31)
at android.os.Looper.loop(Looper.java:154)
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196)
at java.lang.Thread.run(Thread.java:762)
Caused by: java.lang.RuntimeException: Empty Optional cannot be unwrapped
at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:31) 
at android.os.Looper.loop(Looper.java:154) 
at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:196) 
at java.lang.Thread.run(Thread.java:762)