this was well-hidden. (╯°□°）╯︵ ┻━┻

Author: behackl

manim/utils/tex.py

@@ -123,6 +123,7 @@ def _rebuild(self):
             + "\n"
             + self.placeholder_text
             + "\n"
+            + "\n"
             + r"\end{document}"
             + "\n"
         )