R Markdown (beamer) - how to create 2 columns

I am trying to create a presentation using RMarkdown beamer. I want a slide to have 2 columns and this is what I have so far:

---
title: title

author: name
        
date: date

output:
  beamer_presentation:
    theme: Szeged
    slide_level: 2
    includes:
      in_header: header.tex
    keep_tex: true

linkcolor: false
---
    
## TEST

\footnotesize
\justify
:::::::::::::: {.columns}
::: {.column}
- I will write something here tex text text tex text text tex text text
:::
::: {.column}
- And then something here tex text text tex text text tex text text tex text text
:::
::::::::::::::

The header.tex's content is:

\definecolor{mycolorlightblue}{RGB}{103,153,200}
\definecolor{mycolordarkblue}{RGB}{0,70,127}
% add packages
\usepackage{tikz}
\usetikzlibrary{arrows}
\usepackage{tcolorbox}
\usepackage{ragged2e}
% remove 2nd section from header
\makeatletter
\beamer@theme@subsectionfalse
\makeatother
% change colour of lines
\setbeamercolor{separation line}{bg=mycolorlightblue}
% text title
\setbeamercolor{title}{fg=mycolordarkblue}
\setbeamercolor{frametitle}{fg=mycolordarkblue}
% text colour
\setbeamercolor{frametitle}{fg=mycolordarkblue}
% item colour
\setbeamercolor{structure}{fg=mycolordarkblue}
% define colour text
% \usebeamerfont{section title}\color{blue!70!green}\insertsection\par
% no header or footer on first page
\thispagestyle{empty}
% remove title slides at beginning of sections
\AtBeginSection{}
% add page counter to the footer
\setbeamertemplate{footline}[frame number]
% logo of my university
\titlegraphic{%
  \begin{picture}(0,0)
    \put(155,0){\makebox(0,0)[rt]{\includegraphics[]{ALL-ICONS.png}}}
  \end{picture}}

This is the result I am seeing, almost perfect, but the 2nd column starts slight below the first one, as shown below, do you understand why?

correspondent .tex file to the .rmd:

\begin{frame}{TEST}
\protect\hypertarget{test}{}

\footnotesize
\justify

\begin{columns}[T]
\begin{column}{0.48\textwidth}
\begin{itemize}
\tightlist
\item
  I will write something here text text text text text text text text
  text text text text text text text
\end{itemize}
\end{column}

\begin{column}{0.48\textwidth}
\begin{itemize}
\tightlist
\item
  And then something here text text text text text text text text text
  text text text text text text
\end{itemize}
\end{column}
\end{columns}

\end{frame}

The problem is the \justify, it should be \justifying instead (but at the position you use it, it won't have any effect on the text in the columns anyway, so you could also just remove it ...)

---
title: title

author: name
        
date: date

output:
  beamer_presentation:
    theme: Szeged
    slide_level: 2
    includes:
      in_header: header.tex
    keep_tex: true
---
    
## TEST

\footnotesize
:::::::::::::: {.columns}
::: {.column}
- I will write something here tex text text tex text text tex text text
:::
::: {.column}
- And then something here tex text text tex text text tex text text tex text text
:::
::::::::::::::