Issue with WordPress 5.3 and Header Images

Hi Folks,
For your information:
On November 17 www.ads-software.com updated to WP5.3
I can see from my Cloudinary records (Requests and Bandwidth) that a great change took place in my Cloudinary stats from that date.
Confirming the stats change, I have found out today that the WP5.3 upgrade has changed all the links for my header images from the Cloudinary address to my own server address. Hence they are no longer served from Cloudinary.
Sadly I don’t know what other changes are yet hidden.
I have been using Cloudinary V1.1.12 since March 2019 so it is not something that Cloudinary has done to cause this issue.
Please be advises as I am sure this will affect other Cloudinary users too.
Regards and thanks,
Angus