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Hey all!
I have an issue when trying to externalize a tikzpicture. The working example consists of two files. The main file:
\documentclass[oneside, 10pt]{scrreprt}

\usepackage{tkz-euclide,tikz-3dplot}
\usetikzlibrary{external}
\tikzexternalize

\begin{document}
\input{ellipse.tikz}
\end{document ...