R Notebook splits code chunk when rendered

[aloboa]

Rmarkdown and notebooks sometimes render some chunks split: 1 single chunk
in the .Rmd file becomes >1 chunks in the HTML output.

I have found that a question in this regard was asked long ago:
https://stackoverflow.com/questions/57582773/r-notebook-splits-code-chunk-when-rendered
(and an even older question is referenced there), so I reproduce
the formerly reported problem as it is identical to my own:

---
title: "R Notebook"
output: html_notebook
---

```{r}
sample1 <- rnorm(40,10,3)
sample2 <- rnorm(40,10,3)
sample3 <- rnorm(40,10,3)
sample4 <- rnorm(40,10,3)
par(mfrow=c(2,2))
hist1 <- hist(sample1)
hist2 <- hist(sample2)

hist3 <- hist(sample3)
hist4 <- hist(sample4)

https://rpubs.com/beane/521165