AIR NativeProcess standardInput not connecting to app

I encountered this issue a few months back but I never resolved it as I just used command line args instead. I have just returned to it though as I am keen to find out know what's going on.

I have now found that targeting .NET 3.5 or earlier makes it work as expected for me. Switch back to to v4.0 and I get nothing on stdin. I'm not exactly sure where the issue lies, but if you can get by with v3.5 then it might be a solution for you.