[Elecraft] K2 - "INFO 80 " problem

[Giuliano]

I bought a K2 SN 670 to complete my collection Elecraft.
I now have K1, K2 and K3 + P3.
The K2 serial number  is very low and I think some changes are essential 
and others less so. Can anyone tell me what mods are the really important?
I also have a problem that occurs very frequently: when I change band 
+/-, very often comes out "INFO 080". What can I do?
Thanks for the help
I0CG Italy