Buffer source replaces LS sources when starting typing

Hey, I observe an issue with autocompletion. At first I can see what seems to be a correct autocomplete from the LS:

after I type, for a few characters I might be okey:

but eventually the LS source suggestions get replaced by buffer suggestions:

My CocConfig is:
```
{
"elixirLS.dialyzerEnabled": false,
"elixir.pathToElixirLS": "~/.elixir-ls/release/language_server.sh"
}
```