rPivotTable in Shiny showing black areas outside of pivot when scrolled

Question

I an using rpivotTable in a Shiny app

in UI it is inside a tabSetPanel:

 tabPanel("Pivot Table",
           shinycssloaders::withSpinner(
            rpivotTableOutput("pivot_table")
           )
  )

in Server it is updated once the dataframe is loaded and filtered:

output$pivot_table <- renderRpivotTable({ rpivotTable(data = filtered_df(), rows=c("HIGH_LEVEL_GROUP_TERM", "HIGH_LEVEL_TERM", "AE_AS_PREFERRED_TERM"), vals = "SAPPHIRE_CASE_ID_VERSION", aggregatorName = "Count Unique Values", rendererName = "Heatmap", width="100%") })

When I scroll down the page, anything not observable immediately seems to have black on the outside of the pivot table?

I am using "shinydashboard"....