I have a simple R shiny app. Whenever I try and download the table I created I get the following error:

pandoc: Cannot decode byte '\xfe': Data.Text.Internal.Encoding.Fusion.streamUtf8: Invalid UTF-8 stream
Warning: Error in : pandoc document conversion failed with error 1 Stack trace (innermost first):
53: pandoc_convert
52: convert
51: rmarkdown::render
50: download$func [/home/scotcan1/Webshot/app.R#50]
1: shiny::runApp
Error : pandoc document conversion failed with error 1

I don't know what this means. Here is my R/Shiny script and Rmarkdown.

library(shiny)
library(DT)
data(iris)
ui <- fluidPage(
  
  titlePanel("|Species Table"),
  
  sidebarLayout(
    sidebarPanel(
      selectInput("specs",
                  "Number of bins:",
                  unique(iris$Species)),
      downloadButton("download", "Download Report")
    ),
    
    mainPanel(
      tableOutput("specTable")
    )
    
  )
  
)
server <- function(input, output) {
  
  subSpec <- function(x){
    testdat <- iris[iris$Species == x, ]
    return(testdat[1:10,])
  }
  
  reactiveFunction <- reactive({ subSpec(input$specs) })
  
  
  output$reactiveTable <- renderDataTable({ reactiveFunction() }, rownames = FALSE)
  
  output$specTable <- renderUI({
    dataTableOutput("reactiveTable")
    
  })
  
  
  
  output$download <- downloadHandler(
    filename <- "report_file.html",
    
    content <- function(file){
      write.csv(reactiveFunction(), "test_csv.csv", row.names = FALSE)
      params <- list(data = reactiveFunction())
      rmarkdown::render(filename, output_file = file)
    }
  )
}
shinyApp(ui = ui, server = server)

Rmarkdown:

---
title: "Untitled"
output: html_document
params:
  data: NA
---

```{r, echo=FALSE}
data(iris)
library(DT)
datatable(params$data)
```

Any help to interpret the error appreciated.

Andrew