This sounds like it corresponds to this issue
https://github.com/galaxyproject/galaxy/issues/776. Is it possible
that upgrading Galaxy to the latest 15.07 fixes the issue?

On Thu, Oct 8, 2015 at 7:40 PM, Marco Albuquerque
<marcoalbuquerque.sfu@gmail.com> wrote:
> Hello Galaxy Dev,
>
> Consider the workflow found in 'Strelka_Workflow_Sequential' image
>
> Here it is in a different view 'Strelka_Sequential_Workflow_Different_View'
>
> Notice That the first input dataset links to the fetch_interval tool and the
> first preprocess tool. And the second input dataset links only to the second
> preprocess tool.
>
> When you run the workflow, what actually happens is the first input dataset
> goes to the fetch_interval tools and the second input dataset goes to both
> preprocessing tools. (Look at final two images). They have essentially
> executed the same tool twice. Where it should be an execution with a normal
> file and an execution with a tumour file.
>
> Why is this happening? What can I do to fix this?
>
> Thanks,
>
> Marco Albuquerque
>

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