plot_ly boxplot showing wrong x-axis

Suppose I have a list with three slots, but data for slots 2 and 3 are not yet available. When plotting a boxplot with just the first two slots, everything works as expected:

library(plotly)
y <- list("Group 1" = c(105,74,20), 
          "Group 2" = NA_real_, 
          "Group 3" = NA_real_)

boxplot <- plot_ly(type="box")

boxplot %>% 
  add_boxplot(x=y[[1]]) %>%
  add_boxplot(x=y[[2]])

But when trying to plot data for all three slots (where slots 2 and 3 don't have data), then the x-axis label is messed up and the data seems to be messed up as well. (I expected the boxplot to look exactly the same as the one above.)

boxplot %>% 
add_boxplot(x=y[[1]]) %>%
add_boxplot(x=y[[2]]) %>%
add_boxplot(x=y[[3]])

Start by running the issue's R reproduction with plot_ly(type="box") and successive add_boxplot(x=y[[...]] ) calls, comparing two traces with three. Trace how add_boxplot handles NA_real_ inputs and x-axis category assignment. Done means adding empty slots does not change the displayed data or x-axis label compared with the two-slot example.