Limit to same-named labels in Sankey diagram?

Plotly R, MATLAB, Julia, Net Plotly R
1

This data is a subset of a larger set of data in which I want to see sequential flows to the same event (node). It seems however, that there can be a maximum of three nodes with the same label - is this a known feature?

    require(plotly)
    json_data <- list(
      link = list(
        source=0:4,
        target=1:5,
        value=c(71415, 23568, 9328, 4159, 2065)
        ),
      node =list(
        label=c("C", "C", "C", "C", "C", "C"),
        color=c("#4DAF4A", "#4DAF4A", "#4DAF4A", "#4DAF4A", "#4DAF4A", "#4DAF4A")
      )
    )

    p <- plot_ly(
      type = "sankey",
      domain = c(
        x =  c(0,1),
        y =  c(0,1)
      ),
      orientation = "h",
      valueformat = ".0f",
      valuesuffix = "",

      node = list(
        label = json_data$node$label,
        color = json_data$node$color,
        pad = 15,
        thickness = 15,
        line = list(
          color = "black",
          width = 0.5
        )
      ),

      link = list(
        source = json_data$link$source,
        target = json_data$link$target,
        value =  json_data$link$value
      )
    ) %>% 
      layout(
        title = "Flow length should be 6, but only shows 3",
        font = list(
          size = 10
        ),
        xaxis = list(showgrid = F, zeroline = F),
        yaxis = list(showgrid = F, zeroline = F)
      )

    p

I am able to get around this by using spaces around the labels as follows in the node definition

label=c(“C”, “C”, “C”, "C ", "C ", "C ")