IPv6 working in Chrome/Opera but not in Safari/Firefox

[htpc 9]

Hello!

 

I'm facing a strange issue regarding IPv6. On the same machine (macOS Mojave) with latest Eddie client and IPv6, enabled some browser do work with IPv6 (Chromium based) and others  - Safari & Firefox - do not. I tested with IPleak.net and other IPv6 tests online. I also reset both browsers and disabled all extension/plugins to see if any of them would interfere maybe. Still no love for IPv6.

 

What could be causing this? Is this to be expected? Am I missing something?

 

Thank you for your help!