The problem was that the first node was selected automatically and messed up the code that followed. I bypassed it by deselecting it each time:

If nodeText = "Process Order" Then
    tree.selectNode (nodeKey)
    tree.doubleClickNode (nodeKey)
    tree.unselectNode (nodeKey)
    testExtract = session.findById("wnd[0]/usr/tabsTABSTRIP_5115/tabpKOZE/ssubSUBSCR_5115:SAPLCOKO:5120/ctxtAFPOD-KDPOS").Text
    MsgBox testExtract
End If