With respect to the topic of this post and the issue I personally experienced, the firmware appears to have corrected the problem. Thus logically, it was a software related issue.
Now, regarding other aspects of the sound quality that you are speculating about, the Ares II and Pontus II have received almost unanimous acclaim for their sound quality. If the new firmware improves (at least objectively) on that sound, then I'm happy for it.
I suppose I was lucky in that I communicated my issue with Vinshine just as they were preparing to announce the new firmware update. So I got early access. If the sound has improved in any other way, I have not noticed.