An update: PKFirearms told me to send the unit back and they will exchange it. A big thanks to them for the customer service.
I did try the new RRA unit in another lower and encountered the same problem, but I think I discovered the source of the problem is the new trigger/disconnector, and not the hammer as I had previously thought.
When I tried the new hammer with my older trigger/disconnector it worked fine.
When I tried the older hammer with the newer trigger/disconnector the same problem occurred.
The only obvious differences I could see in the older unit (bottom) and the newer one is that the disconnector spring appears to be more compressed in the newer unit..
After measuring I found the area just beneath the disconnector, where the spring is house is .281 inches tall on the newer unit, and .248 on the older one. I don't know if that is what is causing the problem, but it's the only difference I have found.
I not complaining about this because I know PKFirearms will make it right, it's just somewhat of an interesting mystery to me, and the first time I have encountered this type of thing in the dozen ARs I have built.