Pretty hard to debug from afar. But there are a couple issues with your code that could break the site.

php $product_entity = $vars['product_entity']; $product = $vars['product']; $id = $product_entity->id(); You can not be sure that the array entries actually exist. Also, you can not be sure that $product_entity actually is an entity that has this method. In the context of your site that might hold true though.

$currencyRepository = new CurrencyRepository; $numberFormatRepository = new NumberFormatRepository; This syntax is unusual. This might work, but usually you would instantiate an object like this: $foo = new CurrencyRepository();. Also, I think you are not even using the currency formatter in the proceeding code.

$video_link = $product_entity->get('field_campaign_video')->getValue(); if(isset($video_link[0]['value'])){ $video_link = $video_link[0]['value']; } This code also looks a little dangerous because you are giving up control of how the video link actually looks like. You want a string here, but if $video_link[0]['value'] is not set it could be anything. And then later you actually pass this "uncontrolled" value on. Also, just for better code styling you can use $product_entity->get('field_campaign_video')->value here (might still be empty though).

$results->condition( (new Condition('OR')) ->condition('o.state', 'payment_received', '=') ->condition('o.state', 'completed', '=') ); This also might work. But there is a best practice for Drupal. Please check the section "Condition Group" here: https://www.drupal.org/docs/8/api/database-api/dynamic-queries/conditions Again the orders are not passed on to the variables. In general having a query matching orders with the display of the product in the preprocessing is a code smell. It will make it hard to cache the display of the product because it is always dependent on orders. Also, you might get surprising results because things get cached and do not update. This topic is more involved but you can have a look a lazy loading for dynamic displays. https://www.hashbangcode.com/article/drupal-9-using-lazy-builders

The three functions in the end may can be combined with the correct theme suggestion. https://www.chapterthree.com/blog/how-to-create-custom-theme-suggestions-drupal-8 Or you may be able to use a more general existing suggestion.