I’m really happy to see a community of iTunes Match members here, making an effort to resolve this gnarly issue.
I’d implore anyone willing to take the time and speak with AppleCare, or visit the Genius Bar, to request that their rep not only create a standing “ticket / repair,” but to have it *escalated to engineering.*
Apple employees in any form of customer-facing IT service are able to access an internal site that’s dedicated to “emerging issues” concerning apple products and services, and this is about the extent of the visibility they will have into this particular area, as we’ve come to learn that it cannot be resolved with troubleshooting software on the user side.
The most direct form of assistance here will likely be with the engineering team, in which case the proper channels can begin to get involved, and follow through. This is only my experience with the company, but internal strategies change abruptly, and it’s entirely possible that my suggestions are no longer viable, so please do inform me if that is your experience.
No matter what, I’m so grateful to everyone here, having felt lost and alone on iTunes Match Island when this began. I’ll be keeping my eyes on this thread and looking forward to a solution!