41c with 785 registers?

[Pieru]

Hello.
Just arrived on the forum, with the same question. Old post !

I’ve found a hp-41cv in my father’s home.
Just running in prgm mode, showing a ‘flying goose’ on left digit, prgm flag is on.
R/S stops the program for 1 sec, showing 0, E00 then MEMORY LOST and starts again.
R/S then SST shows 00 reg 785, prgm flag is off. Then any other keystroke displays the function symbol + or resets the calculator.
Hard reset shows MEMORY LOST and prgm starts again.

I’ve tried to discharge the backup capacitor : unsuccessfull.

Any help would be appreciated.
Thanks