The elixir compiler runs jobs in parallel so it could be triggering a concurrency issue due to differences in the memory model between x86 and ARM. I’ve peered at the Erlang VM code and it looks like they are using primitives that are aware of the differences but they might not have covered everything.

Until recently there was a concurrency bug in the VM that would trigger on elixir compiles that would cause compilation to hang on both x86 and ARM.