Leaflet not generating properly in dynamic R markdown document - r

Question

I have asked this question before here.
Initially the focus was on a point map, which the answer fixed. However looking at clustered and heatmaps, the issue persists.
Point generates fine (fixed via previous question)
Clustered do not appear on map
Heatmap doesn't show at all (whitespace)
Minimal code example:
library(tidyverse)
library(leaflet)
library(leaflet.extras)
leaflet()
long <- as.numeric(c("0.005638", "0.005648", "0.005658"))
lat <- as.numeric(c("51.62879", "51.62889", "51.62879"))
data1 <- data.frame(long, lat)
filtered_list <- 1:3
cat("## Tabs {.tabset .tabset-fade .tabset-pills}", "\n")
for (estates in filtered_list){
cat("###", estates, "\n")
cat("\n\n\n")
cat("This is where the map will go ")
cat("1 ")
# generate leaflet plot
page <- htmltools::tagList(
leaflet() %>%
addTiles() %>% # Add default OpenStreetMap map tiles
addMarkers(lng=data1$long, lat=data1$lat)
)
cat(as.character(page))
cat("2 ")
page1 <- htmltools::tagList(
leaflet() %>%
addTiles() %>% # Add default OpenStreetMap map tiles
addMarkers(lng=data1$long, lat=data1$lat, clusterOptions = markerClusterOptions())
)
cat(as.character(page1))
cat("3 ")
page2 <- htmltools::tagList(
leaflet() %>%
addTiles() %>% # Add default OpenStreetMap map tiles
addMarkers(lng=data1$long, lat=data1$lat) %>%
addHeatmap(
lng = data1$lat, lat = data1$long,
blur = 20, max = 5, radius = 40
)
)
cat(as.character(page2))
}
The maps render fine in R Studio, e.g.