Overriding exception.hbs from site customization

I’m trying to override exception.hbs from a site customization, like so:

<script type='text/x-handlebars' data-template-name='exception'>
    <div class="container">
      <div class="error-page">
        <div class="reason">Oops, looks like we flew into a wall!</div>
        <div class="url">
          {{i18n 'errors.prev_page'}} <a {{bind-attr href=requestUrl}} data-auto-route="true">{{requestUrl}}</a>
        </div>
        <div class="desc">
          {{#if networkFixed}}
            <i class="fa fa-check-circle"></i>
          {{/if}}
    
          {{desc}}
        </div>
        <div class="buttons">
          {{#each buttonData in enabledButtons}}
            {{d-button icon=buttonData.icon action=buttonData.action label=buttonData.key class=buttonData.classes}}
          {{/each}}
          {{conditional-loading-spinner condition=loading}}
        </div>
      </div>
    </div>
</script>

(in reality there’s more customization I have planned, but this is just where I am right now)

Anyways, for some reason none of the local handlebars variables are accessible so the “Try Again” button etc. don’t work. Is it possible to get at 'em? It seems weird that they wouldn’t be there, so maybe this is a bug? I tested by rendering {{reason}}

Edit: never mind, the default fails too when I use /exception to test, but works on other pages. Feel free to lock this, I’m just an idiot