I have owned a HP12C progamable calculator for the last 15yrs with nil faults but had to replace as the buttons stopped functioning. So in Oct 2015 I purchased a new HP12C programmable calculator - in September 2016 a fault [Pr Error]developed and now doesn't operate.
If I purchase a new HP12C Platinum programmable calculator - which I have been told ther is nil stock in the warehouse, does the problem still exist or has the issue of the [Pr Error} been addressed and rectified in the latest versions.
All the new HP-12C calculators are sensitive to low battery. When you get "PR Error" usually a replacement of the batteries will solve the problem. Use a good brand from a reliable source - there are many low quality rip-off batteries out there.
Your original 12C contained a "884 kilo-Hz" processor. The new one contains a "32 mega-Hz" processor. That means it is over 32 times "faster" then the original processor. Calculations which would take a minute or so with your original 12C are basically instant with the new one.
Nobody sells processors that use that little power any more though. This is why the new 12C has a faster processor in it (which is still very "slow" compared to modern standards however). The downside is that it is not as battery efficient. As Bart has explained, all you need to do is put in a new battery and you should be good.
Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.