This is very weird, I have many sites hosted with my EE -- some with SSL enabled and some not but i have never experienced what you describe.
Perhaps you can post a list of urls/domains that doing this redirection and some of your config files, b/c without seeing them it's really hard to help you troubleshoot the issue. Are these sites WP, or just HTML/PHP? Any caching used with these sites?
I'm inclined to believe it;s more of a misconfiguration issue then a EE bug.
Also what are your DNS config for these sites?