Hiya, one of the mentioned thread folks here. Thanks for making this post to help bring awareness to everything!
I did submit a support ticket with screenshots and details over my issues and was met with the "We will forward your report to the development team so that they can investigate the issue. However, we may be unable to personally email you about the investigation but any major updates may be announced on our website and/or forums" response. While its sadly something the dev team needs to look into, I do recommend to keep sending in tickets with screenshot proof and as much details as you can give.
Bonus issue that I did report to support that I did not list in my thread is that the "Bittersweet Symphony" achievement is also locked as I completed the Echoes of a Song quest before the Achievement issues were fixed for Musician. Minor as it blocks me from a title, but still one to bring up.