Externalization of tikz-feynman environment inside math environment spawns multiple figure files

[Turgon-Aran-Gondolin]

I was using the following code to externalize the tikz-feynman diagrams

\usetikzlibrary{external}
\tikzexternalize[shell escape=-enable-write18,prefix=./,system call={lualatex \tikzexternalcheckshellescape -halt-on-error -interaction=batchmode -jobname "\image" "\texsource"},up to date check=diff]

When the diagrams are in figure environment everything works fine. But those in align environment were generated twice. So my working dir is now filled with duplicated feynman diagrams. Is there any way to resolve this?

[JP-Ellis]

This is very odd, though I doubt it's an issue with TikZ-Feynman and probably is an issue upstream in TikZ itself. Consider raising this issue with pgf-tikz/pgf.