DownloadManager IllegalStateException creating a download in DIRECTORY_DOWNLOADS

Question

Firstly, there are a lot of questions on this subject, but none reflect my issue. I have for example read this and this.

The issue that I have, is that in an extremely small number of cases, my function to setDestinationInExternalPublicDir results in the following stack trace:

Fatal Exception: java.lang.RuntimeException: Unable to start receiver com.onlinetvrecorder.otrapp2.listeners.DownloadUpdateReceiver: java.lang.IllegalStateException: Unable to create directory: /mnt/sdcard/Download
       at android.app.ActivityThread.handleReceiver(ActivityThread.java:2274)
       at android.app.ActivityThread.access$1500(ActivityThread.java:131)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1272)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:4791)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
       at dalvik.system.NativeStart.main(NativeStart.java)
Caused by java.lang.IllegalStateException: Unable to create directory: /mnt/sdcard/Download
       at android.app.DownloadManager$Request.setDestinationInExternalPublicDir(DownloadManager.java:496)
       at com.myapp.Utils.download(SourceFile:752)
       at com.myapp.Receiver.onReceive(SourceFile:20)
       at android.app.ActivityThread.handleReceiver(ActivityThread.java:2267)
       at android.app.ActivityThread.access$1500(ActivityThread.java:131)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1272)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:4791)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
       at dalvik.system.NativeStart.main(NativeStart.java)

I am using a standard Environment constant to tell the DownloadManager where to save the file.

android.app.DownloadManager dm = (android.app.DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);

DownloadManager.Request request = new DownloadManager.Request(Uri.parse("url.to.file.ext"));
request.setMimeType("mime/type");

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
    Utils.setDownloadRequestVisibility(request, android.app.DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}

request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "file.ext");
request.setTitle(context.getString(R.string.download));

dm.enqueue(request);

As previously stated, there are perhaps not even 1% of users getting this error. What could be causing it?

Answer 1

In the course of writing my question, I noticed that I had probably just solved the issue myself. I was going to write what the offending device model was, but on Crashlytics it displayed "Unknown". I clicked upon that, and the following model was revealed: GI I9500 TMMARS. Running Android 4.

TMMARS appears to be software from Trend Micro.

Trend Micro Mobile App Reputation Service or TMMARS is a cloud-based service that automatically identifies mobile threats based on app behaviors.

It is extremely likely that the system is not behaving as the App expects it to, simply because it is a threat detection environment.

Example crash report: