ggplotly in shiny producing lines in scatterplot

[Adam Goodkind]

In the code below, the plot changes depending on whether "All Typists" is selected or not. When it is selected, the app looks like this, a scatter plot with a trend line:

However, when the checkbox is deselected, the plot looks like this, adding lines between the points. It should be noted that this is not a trend line. When there are more points, there are lines between all of them.:

Is this a bug in shiny/ggplotly? Or is it an issue with my code? I've provided a minimal example below

    library(tidyr)
    library(dplyr)
    library(reshape)
    library(shiny)
    library(plotly)
    library(ggplot2)
   
    df <- as.data.frame(list("UserID"=c(1,1,1,1,2,2,2,2),
                              "QuestionID"=c(4,4,5,5,4,4,6,6),
                              "KeystrokeRate"=c(8,4,6,15,8,6,7,8),
                              "cumul.ans.keystroke"=c(3,7,4,5,11,14,3,9),
                              "Relative.Time.Progress"=c(0.1,1.0,0.4,1.0,0.8,1.0,0.8,1.0)
                        ))
   
    trendLineOptions = c("All Selected User's Answers"="allThisUser",
                         "All Typists"="allTypists"#,
                        )
   
    ui <- (fluidPage(
      sidebarLayout(
        sidebarPanel(
          selectInput("userInput","Select User", sort(unique(df$UserID)),
                      selected = sort(unique(df$UserID))[1]),
          uiOutput("answerOutput"),
          checkboxGroupInput("trendsInput", "Add Trend Lines",
                             choices=trendLineOptions,
                             selected="allTypists")#,
        ),
       
        mainPanel(
          plotlyOutput("mainPlot")#,
        )
      )
    ))
   
    server <- function(input, output, session) {
     
      # filter only based on selected user
      filteredForUser <- reactive({
        try(
          df %>%
            filter(
              UserID == input$userInput
            ), silent=T)
      })
     
      # filter for both user and answer
      filteredFull <- reactive({
        try (
          df %>%
            filter(
              UserID == input$userInput,
              QuestionID == input$answerInput
            ), silent=T)
      })
     
      # filter answer choices based on user
      output$answerOutput <- renderUI({
        df.u <- filteredForUser()
        if(!is.null(df)) {
          selectInput("answerInput", "Select A Typing Session",
                      sort(unique(df.u$QuestionID)))
        }
      })
     
      output$mainPlot <- renderPlotly({
       
        # add trend line based on this user's data
        addUserTrendLine <- reactive({
          if (class(filteredForUser()) == "try-error" ||
              class(filteredFull()) == "try-error") {
            return(geom_blank())
          }
          if ("allThisUser" %in% input$trendsInput) {
            g <- geom_smooth(data=filteredFull(), inherit.aes=F,
                             aes(x=Relative.Time.Progress,y=cumul.ans.keystroke),
                             method='lm')
          } else {
            g <- geom_blank()
          }
          return (g)
        })
       
        # add trend line based on all data
        addAllUsersTrendLine <- reactive({
          if (class(filteredForUser()) == "try-error" ||
              class(filteredFull()) == "try-error") {
            return(geom_blank())
          }
          if ("allTypists" %in% input$trendsInput) {
            g <- geom_smooth(data=df, inherit.aes=F,
                             aes(x=Relative.Time.Progress,y=cumul.ans.keystroke),
                             method='lm')
          } else {
            g <- geom_blank(inherit.aes=F)
          }
          return (g)
        })
   
        if (class(filteredForUser()) == "try-error" ||
            class(filteredFull()) == "try-error") {
          return(geom_blank())
        } else {
          # plot scatter points and add trend lines
          gplot <- ggplot(data=filteredFull(),
                          aes(x=Relative.Time.Progress,y=cumul.ans.keystroke)) +
            geom_point(aes(size=KeystrokeRate,colour=KeystrokeRate)) +
            addUserTrendLine() +
            addAllUsersTrendLine()
          g <- ggplotly(p=gplot, source="main")
        }
      })
     
    }
   
    shinyApp(ui, server)