I've got in a longtable with one column split into two by multicol. Somehow multicol adds a white line before starting with the text.
![example of white line](https://i.stack.imgur.com/CHVlC.png)

My MWE:

```
\documentclass{article}
\usepackage{longtable}
\begin{document}
.
.
.
\begin{longtable}{|l|X|}
1 & \begin{multicols}{2}1. text \newline 2. text \newline 3. text \newline 4. text \newline 5. text \newline 6. text  \end{multicols} \\
\end{longtable}
\end{filecontents}
\LTXtable{\textwidth}{longtable.tex}

\end{document}

```