Scroll bar not loading in flexdashboard with text

Question

I am reading in text files from R in R-Markdown using the flexdashboard. The text file however is larger than the box. Typically the box creates a scroll bar on the right side. However with text the scroll bar isn't loading.

---
output: 
      flexdashboard::flex_dashboard:
        theme: flatly
        social: menu
        orientation: columns
        vertical_layout: fill
---

Title1 
=====================================  
Column 
-------------------------------------

### Subslide1
```{r code=readLines('text_example.R')}
```

`r df$text`

### Subslide2

```{r, echo=FALSE}
kable(dx)
```

The variables df$text is a text file I am reading in through R. dx is just a table. I do not want to force the size of each section because the text can vary in length and I don't want to change the width of the table box.

Thanks!