Hi
The developer of yoursite found that it was related to 4SEO, due to the fact that it stored the initial URL.
4SEO must be configured at all times with the site current URL. The actual site URL is needed for various SEO purpose and cannot be guessed. Set the current website address under Pages | Settings | Site | Website home address
I clicked on a link on the cloned site, I was redirected to the initial site.
This would only happen due to 4SEO if you configured it to Always redirect to site main address (under Pages | Settings | Site).
That option is disabled by default and should not be enabled unless you have a good reason.
I uninstalled 4SEO on the clone and it produces an 404 error
4SEO does not cause 404 errors. It's an SEO tool, it does not respond to requests. Especially if it's been uninstalled! It's not there, it cannot cause any issue!
I can't be sure as I don't know how exactly your site is doing cloning but the first thing that comes to mind is that you installed your clone in a subfolder of your main site, therefore you mayb have to modify the .htaccess file of your main site to let the subfolder site work.
Best regards
Yannick Gaultier
weeblr.com / @weeblr