~ MUCH appreciated buddy!
The issue resolved in that fix, was related to an invalid regular expression match against options configured within s2Member's UI panel for Auto-Unsubscribes. A permanent fix will be pushed out in the next release, but the patch I provided you with should resolve the problem as well, in its entirety.
Regarding the new issue you reported.
6.) Checked in Mailchimp to find the subscription to the PREMIUM list was GONE (deleted from list which is great).
7.) HOWEVER the user (now a subscriber) was not set to the FREE members list in mailchimp.
Did this person confirm the subscription to the new list yet?
Perhaps we need to NOT require a confirmation in this specific scenario?