UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36

Steps to reproduce the problem:
1. go to https://www.currys.co.uk/gbuk/phones-broadband-and-sat-nav/mobile-phones-and-accessories/mobile-phones/samsung-galaxy-s8-64-gb-black-10161802-pdt.html
2. save page for overrides and enable overrides
3. check console for "No 'Access-Control-Allow-Origin' header" error. 

What is the expected behavior?
I would expect the page https call to be re-routed to my local file and to return these contents (modfied if required).

What went wrong?
Access to Script at 'https://media.flixcar.com/delivery/js/inpage/2162/en/mpn/10161802?&=2162&=en&mpn=10161802&ssl=1&ext=.js' from origin 'https://www.currys.co.uk' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://www.currys.co.uk' is therefore not allowed access.

Did this work before? N/A 

Chrome version: 67.0.3396.87  Channel: stable
OS Version: 
Flash Version: Shockwave Flash 30.0 r0

This behaviour is consistent, however on some other files from the same origin I am able to get the page re-routed to my local folder for overrides - intermittently. 

I have tried launching chrome with web security disabled, but that has not solved the issue.