Featured Images disappear when you edit a listing if you use a CDN that hosts external images

If you are using a CDN to host external images, the featured image or images originally added to the listing disappears.

The issue is when you want to edit the submission. If you click 'save' all seems fine, when you go to the front end and refresh the featured image disappears. I have tried with with two different CDN plugins

I think this issue is slightly different from wpjm rejecting external images on submission. This is wpjm rejecting external images on edit without displaying an error.

To replicate,
1. Download any CDN external image plug that changes the URL of your images so they are sourced from the CDN URL. I used 'WP Offload Media Lite' and also used 'Leopard - Wordpress offload media.

2. Turn all unecessary plugins off only the plugins that work with wpjobmanager'
3. Ensure you are running the latest version of wordpress 5.5.1
4. Create a listing with a featured image and submit
5. Go to front end and check. Featured image is there and if you inspect the URL of the image, it points to the CDN URL.
6. Now go back and click edit the listing, and just save, you don't necessarily have to make any changes, but click save again.
7. Now go back to the listing. Featured image disappears.

**WordPress Environment**
- WordPress Version: 5.5.1
- WP Job Manager Version: 1.34.3
- PHP Version: 7.2
- Other important details: Used default wordpress theme and listable theme on codecanyon

No repository file, test, or entry point is named. Reproduce the issue with WordPress 5.5.1, WP Job Manager 1.34.3, PHP 7.2, and either listed CDN plugin, then trace the front-end listing edit/save flow. Done means saving an unchanged listing preserves its externally hosted featured image and does not silently discard it.

Written by the indexing model from the issue text.