EHS is stopping application from writing to external storage?

We have Enterprise Home Screen v2.3 installed on an Android MC40 running KK.  When we are trying to write to a file on the sdcard from within our application, no errors or exceptions are thrown in code and everything looks as if the file has been created, but it isn't.  No file is created.  I have tried this on a TC55 running KK without EHS, and it works as expected.  The file is created and written to correctly.

 

We are writing to /sdcard/ (the public external storage directory)

 

I cannot find any options in the EHS config that restrict the ability to write to external storage, but everything seems to be telling me that is exactly what is happening.  Is there an option I am not seeing in the user guide?  What is restricting me?

 

Thanks.