I support your request. Had the exact same problems in the past, but I was able to use the same password for both services. This fixed the issue for me and login to both services since then worked like a charm.
The subscriber portal is a connected to Aras own internal Innovator instance. It might help to change your password in MyInnovator to improve the login to the subscriber portal page. But I am not 100% sure about this one.
The community forum is a separate engine, but maybe when login in to community via the common address, the background service checks if you are partner, subscriber or free-user. They did a couple of modifications to the subscriber portal recently. Maybe this had some effects. I actually wait for Aras to finally provided the enhanced detailed road map in the subscriber portal.
