Eager loading in Laravel 9 vs 5

Question

I am upgrading a project from Laravel 5 to Laravel 9, and one of the Controller methods seems to break and I cant figure out why. It works perfectly fine in Laravel 5, I get all the models returned. It fails when trying to load the 'liveConfig' and 'draftConfig' models.

Error

PHP Error:  Call to a member function addEagerConstraints() on null in /var/www/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Builder.php

Controller

public function show($siteId)
{
    return auth()->user()->editing()->findOrFail($siteId)->augmented();
}

Relationships

public function liveConfig()
{

    if (!$this->theme) {
        return;
    }

    return $this->hasOne(LiveConfig::class)->where('status',
        'live');
}

public function draftConfig()
{
    if (!$this->theme) {
        return;
    }

    return $this->hasOne(LiveConfig::class)->where('status',
        'draft');
}

Eager Loading method

public function augmented()
{
    $this->load([
        'theme',
        'theme.renewalPlans',
        'subscription',
        'subscription.nextSubscription',
        'liveConfig',
        'draftConfig',
    ])->append('open_invoices_count', 'cmsStyling', 'cmsStylesheets');
}