When adding link_to_add_association page doesn't render

Question

Here is my code:

The view:

<h1>New Standup</h1>

<%= form_for @standup do |f| %>
Yesterday Items:
<ul>
    <%= f.fields_for :yesterday_items do |f1| %>
        <li>
            <div class="nested-fields">
            <%= f1.label :item %>
            <%= f1.text_field :item %>
            <%= link_to_remove_association 'Remove item', f %>
            </div>
        </li>
    <% end %>
</ul>
<div class="links">
    <%= link_to_add_association 'Add Item', f, :yesterday_items %>
</div>

Today Items:
<ul>
    <%= f.fields_for :today_items do |f2| %>
    <li>
        <%= f2.label :item %>
        <%= f2.text_field :item %>
    </li>
    <% end %>
</ul>
<%= f.submit %>
<% end %>

<%= link_to 'Back', standups_path %>

The controller:

class StandupsController < ApplicationController

def index
    @standups = Standup.all
end

def new
    @standup = Standup.new

    @standup.yesterday_items.build
    @standup.today_items.build
end

def create
    @standup = Standup.new(standup_params)

    if @standup.save
        redirect_to standups_path
    else
        render 'new'
    end
end

def edit
end

def update
end

def destroy
end

private
def standup_params
    params.require(:standup).permit(yesterday_items_attributes: [:id, 1, :item, _:destroy], today_items_attributes: [:id, 1, :item, :_destroy])
end

end

And the model:

class Standup < ActiveRecord::Base
has_many :yesterday_items, dependent: :destroy
has_many :today_items, dependent: :destroy
accepts_nested_attributes_for :today_items, :reject_if => :all_blank, :allow_destroy => true
accepts_nested_attributes_for :yesterday_items, :reject_if => :all_blank, :allow_destroy => true
end

When I remove the line: <%= link_to_add_association 'Add Item', f, :yesterday_items %> the page renders with the remove assosiation link, which does nothing, but at least it shows for now, but when adding the line the page doesn't render anymore. I have installed and updated the cocoon gem and add //= require cocoon to the aplication.js file. I have no idea what the problem could be.

UPDATE:

I wrote a partial which looks like this:

<div class="nested-fields">
    <%= f.label :item %>
    <%= f.text_field :item %>
    <%= link_to_remove_association 'Remove item', f %>
</div>

And am calling it with:

<%= render "yesterday_form", :f => f1 %>

But the behavior doesn't change, the page still wont render when adding <%= link_to_add_association 'Add Item', f, :yesterday_items %> and the link_to_remove_association still doesn't do anything.