Hi Andrea,
Yes this is exactly the case : some domains are A+ and others are D with both the same configurations…
I noticed on some domains that the WP Rocket cache plugin was interacting with the scan, it was D before i emptied completely the cache and A+ afterward, but not always and not for long either.
This is very intriguing to me because i dont’t see why that should be as, as far as i understand, HSTS only deal with .htaccess and shouldn’t be concerned with content.
Thanks for your time