Note that DSLReports user "Iscream" apparently works for Callcentric. His posts get a bit testy and defensive, but understandably so. CC has gone out of their way to help explain and diagnose it. He points to what I am pursuing with Google at this time; a possible problem with what he calls an "aggregator", or transit carrier.
In simpler terms, someone calls your Google Voice number. Next, Google is not a regulated telephone company (CLEC). So, it buys telephone network services from a variety of carriers, both to terminate numbers (host them on a phone switch, so that it can be called by other numbers), and to transport the forwarded outbound calls to your forwarding phone numbers' destinations. So at this point, Google's system then selects a transit carrier to send the call to your Callcentric DID. We think that the CID / CNAM is getting altered in that path, before it reaches CC.
On a related note, Iscream describes the business and technical decisions that CC has made to make call quality and reliability a priority, at some added expense over the competition. There's been a lot of focus here on this forum on finding the very cheapest internet telephone service provider, with some charging much lower per-minute rates. This is an example of "you get what you pay for". I've been accused of being a shill for CC, but I simply appreciate their approach, and support it with my business. Other folks may be satisfied with a lower-priced solution; to each his/her own.
Google, by the way, does use multiple carriers, but its focus is also on reliability and call quality, and it is doing a lot of work internally to optimize both those things.
Again, I don't know if or when I can get this fixed, but I'm devoting some time and resources now to focusing on it.