Bug Location: Vessel.vb, RunDynamicModel(),
this is code that needs to be fixed

        For i = 0 To 5
            If Me.GraphicObject.InputConnectors(i).IsAttached Then
                Dim imsx = GetInletMaterialStream(i)
                If imsmix Is Nothing Then imsmix = imsx.CloneXML
                imsmix = imsmix.Add(imsx)
            End If
        Next

Problem: The first inlet stream is added twice:

1. First: imsmix = imsx.CloneXML (contains stream 1)
2. Then: imsmix = imsmix.Add(imsx) (adds stream 1 AGAIN)

Evidence: Material balance around separator consistently shows
outlet/inlet ratio of 2.00xxx (within numerical tolerance).

Fix: Add Else clause to only Add() subsequent streams, not the first one.

I noticed the recent commit (10 days ago) attempted to address this but
accidentally made it worse by adding a third addition. The fix is
straightforward - happy to submit a PR if helpful.

This bug affects all dynamic separator simulations and breaks fundamental
material balance.