File Passthrough when using a Router getting ERROR #5005

Hello

I am writing a simple routing interface that picks up files from a share using File.InboundAdapter.

I am then using PassthroughService and passing it to a router.

The Router is using Ens.StreamContainer to then get the filename.  I have then used contains to pick out part of the filename.

and then pass it to another simple passthrough operation to another share.

If I do a direct link without using the router it works fine and I get no errors, once I direct the messages through the router I am getting ERROR #5005  Cannot open file, it does however write a file to the share but the file is a corrupt pdf I cannot open.

Is there something I have missed or a reason I can't do this? 

Thanks

Lorraine