HP-67 weird behavior after reading a card

[albertofenini]

Hi everyone

we are looking for advice ...
this unit works well, though we haven't tried to input manually a program
reading a card, in this example SD-04A, works fine too
when trying to input some data, in this case we wanted to find out the weekday for a certain date,
it behaves erratically as shown in the picture
other CPU boards coupled with this card reader and this chassis have no problems at all ...
what could it possible be wrong ?

pictures can be found here : HP-67 acting weird after reading a card

thanks in advance and take care !!