Most of the functionality for this extension comes from ElixirLS: https://github.com/JakeBecker/elixir-ls
Please try the ElixirLS extension for VS Code before filing your issue. If your issue is reproducible in that extension, please file it on ElixirLS here: https://github.com/JakeBecker/elixir-ls/issues