I have the same Issue on a Samsung GT-I9301I with 4.4.2.
E/AndroidRuntime: FATAL EXCEPTION: main
Process: ch.xxxxx.app, PID: 27848
java.lang.VerifyError: de/xxxx/network/ErrorHandlingCallback$AjcClosure1
at de.xxxx.network.ErrorHandlingCallback.onUpdateUi(ErrorHandlingCallback.java:84)
at de.xxxx.network.ErrorHandlingCallback.onResponse(ErrorHandlingCallback.java:67)
at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:68)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5476)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
I have the same Issue on a Samsung GT-I9301I with 4.4.2.