Issues with assigns and push_events

Context

I’m having some issues with getting a LiveView hook to fire when I assign things to the socket first. I have the following event handler in my live file (setup_live.ex):

def handle_event("save_personal_details", params, socket) do
  game_state = "setup_skills"
  socket = socket
  |> assign(:player, to_form(params))
  |> assign(:skills, to_form(@skills))
  |> assign(:game_state, game_state)
  |> push_event(
    "submit_player_personal_details",
    %{player: params, game_state: game_state}
  )

  {:noreply, socket}
end

In this case both params and @skills are just maps and will render correctly in a form (I mention this as I thought something may be going wrong with to_form but this doesn’t seem to be the case).

In a component I have a form with phx-hook="SetupPersonalDetails" and phx-submit="save_personal_details". So far so good, this event handler is called when I submit the form.

I then have a SetupPersonalDetails hook that looks like this:

export const SetupPersonalDetails = {
  mounted() {
    this.pushEvent("restore", {
      player: JSON.parse(localStorage.getItem("player")),
      game_state: localStorage.getItem("game_state") || "setup_personal_details"
    })

    this.handleEvent("submit_player_personal_details", playerPersonalDetails => {
      console.log('Updating player personal details...')
      localStorage.setItem("player", JSON.stringify(playerPersonalDetails.player))
      localStorage.setItem("game_state", playerPersonalDetails.game_state)
      console.log('Player name submitted')
    })
  }
}

The Problem

My hook never handles the submit_player_personal_details that’s emitted - unless I remove the assigns from my event handler. If I change my event handler in my live file to:

def handle_event("save_personal_details", params, socket) do
  game_state = "setup_skills"
  socket = socket
  |> push_event(
    "submit_player_personal_details",
    %{player: params, game_state: game_state}
  )

  {:noreply, socket}
end

in other words, remove the pipes into assigns, the JavaScript Hook runs and writes to localStorage correctly. What am I doing wrong here? I’m a bit of a Phoenix/Elixir novice, any help appreciated!