Problems with admin styles/js scripts

I have an odd issue.I use a duplicator installers to move a sites from development to production quite ofter, mostly without problems. But now on 2 separate occasions we ran into the problem that after the installer had deployed and we logged into the admin panel, the admin pages looked like a site without css. (errors in the console show loading 403 errors on load-styles.php and load-scripts.php). This is solved with adding define(‘CONCATENATE_SCRIPTS’, false); to the wp-config file. The first time was a rushed migration from a server that wasnt working so well, and the source and destination server were very different in configuration.(so we didnt look any further the first time).

Normally I would say, remake the package and try again. But this had no effect.
I also used the same package to install it on another test domain and subdomain. Both worked without a problem. To me that would ‘clear’ the package as the problem.

It is also odd that a couple of other sites I moved had no trouble.

All these sites came from the same server and were moved to the same server as the ‘problem site’. All domains are the same in terms of apache and PHP settings. A handfull of moved sites even have identical theme and plugins as the ‘problem’ site that had issues. And the source and destination server are identical in setup. Same php version, latest plesk updates installed, same packages etc.

The subdomain is on the same user as the development domain but the other test domain is a real domain, just like the ‘problem’ domain.

The only difference I know between the problem site and my tests with the same installer on other test domain and subdomain is that the ‘problem’ domain has a ‘real’ ssl certificate and the test domains were both put on a quick let’s encrypt certificate.

The rest is the same. What could be the problem? Is there anything else I can test.