Sankey labels appear at strange locations

In vertical sankeys, mouseover labels of flows appear at strange locations, some of them outside the drawing area.

See here:

library(plotly)
library(rjson)

json_file <- "https://raw.githubusercontent.com/plotly/plotly.js/master/test/image/mocks/sankey_energy.json"
json_data <- fromJSON(paste(readLines(json_file), collapse=""))

p <- plot_ly(
  type = "sankey",
  domain = list(
    x =  c(0,1),
    y =  c(0,1)
  ),
  orientation = "v", # this is the only change to the original example
  valueformat = ".0f",
  valuesuffix = "TWh",
  
  node = list(
    label = json_data$data[[1]]$node$label,
    color = json_data$data[[1]]$node$color,
    pad = 15,
    thickness = 15,
    line = list(
      color = "black",
      width = 0.5
    )
  ),
  
  link = list(
    source = json_data$data[[1]]$link$source,
    target = json_data$data[[1]]$link$target,
    value =  json_data$data[[1]]$link$value,
    label =  json_data$data[[1]]$link$label
  )
) %>% 
  layout(
    title = "Energy forecast for 2050<br>Source: Department of Energy & Climate Change, Tom Counsell via <a href='https://bost.ocks.org/mike/sankey/'>Mike Bostock</a>",
    font = list(
      size = 10
    ),
    xaxis = list(showgrid = F, zeroline = F),
    yaxis = list(showgrid = F, zeroline = F)
  )

Result:

This is the mouseover of the flow currently shaded in dark grey. In general, labels of flows to the left of the plot appear at rather correct locations and labels of flows to the right of the plot are off or do not display at all.

> version
               _                           
platform       x86_64-w64-mingw32          
arch           x86_64                      
os             mingw32                     
system         x86_64, mingw32             
status                                     
major          3                           
minor          6.1                         
year           2019                        
month          07                          
day            05                          
svn rev        76782                       
language       R                           
version.string R version 3.6.1 (2019-07-05)
nickname       Action of the Toes      

> packageVersion("plotly")
[1] ‘4.9.1’

Commencez par exécuter l’exemple Sankey fourni de R plot_ly avec une orientation verticale et comparez les étiquettes au survol sur toute la zone de dessin. Suivez le point d’entrée du positionnement des étiquettes au survol des flux Sankey et vérifiez que les étiquettes restent alignées sur leurs flux, y compris les liens à droite ; ajoutez ou exécutez une vérification de régression si l’emplacement de test pertinent est trouvé.