HP 15c Limited Edition OLD batteries

[ytterligare]

WAS : "Really disappointed by HP : 15c Limited Edition"

I know, I read elsewhere people are having problem with this calc's keyboard.

I'm not, or at least I don't think it is the keyboard.
I purchased this calc brand new in 2011, used it for maximun 10-20 hours, then stored it away in a dry place ( home ).
Reopened the box today, I started to use it for fun, and this happened :

https://youtu.be/iX1fBrKA1pA

Now, the batteries seem to be in good shape ( they both measure 2.9 V ), I've tried either the "ON+"-" reset method, the paperclip on the back and shorting the battery terminal , but nothing seems to help : after the "Pr Error", which sometimes is "corrupted", the behaviour is the same.
I'm really disappointed, since the calc is technically almost brand new....anyone any idea ?

Tnx
A.