Hi Aubrey,
I have not used previous versions, so I can't say whether this is an issue with the new build or with my radio.
I expect this is the case. There are apparently two nearly identical versions of the PX-2R floating around with no distinguishing features other than a serial number range difference. As a result, supporting these two models in CHIRP simply by attempting to guess which version is being used it extremely error-prone and would also be non-trivial in the amount of work required to do it. Even Puxing's own software has two versions, one of which works with either radio, with no real explanation of why or how to determine which is which.
So, I made the call to not invest the time trying to make CHIRP work for both of them since you are only the second person I've heard from with the "other" version of the radio. The first was keen on getting rid of his radio anyway. Since I _think_ you have the older version, I'm not sure it's worth the time and effort for just a few users.
Sorry for the bad news, but I hope you understand...