Sankey Paths can be plotted outside the plot area

When a link is plotted from a source node to the right of a target node on the diagram (the path loops around and goes upstream), then the path can be plotted outside the plot area. I have data that does this to such an extent that the hover information is not showing.

library(plotly)

fig <- plot_ly(
  type = "sankey",
  orientation = "h",
  
  node = list(
    label = c("A1", "A2", "B1", "B2", "C1", "C2"),
    color = c("blue", "blue", "blue", "blue", "blue", "blue"),
    pad = 15,
    thickness = 20,
    line = list(
      color = "black",
      width = 0.5
    )
  ),
  
# With your example, I added the 7th values in each of the vectors in the link list.
  link = list(
    source = c(0,1,0,2,3,3,4),
    target = c(2,3,3,4,4,5,3),
    value =  c(8,4,2,8,4,2,40)
  )
)
fig <- fig %>% layout(
  title = "Basic Sankey Diagram",
  font = list(
    size = 10
  )
)

fig

Run the provided R example with the Sankey link from a right-side source to an upstream target, then inspect the Sankey rendering entry point responsible for path placement. Done means the looped path remains within the plot area and its hover information is visible.