After separating the original keyboard's layers at the shift buttons and measuring continuity between the top and bottom traces it turned out that the keyboard and the shift column common (COL0) is broken. The tracks at the left shift seems to be corroded, so I assume that the reason of the dislemanting of the whole notebook was a water accident.

I almost decided to give up on this architecture (and move to a Thinkpad R60 keyboard with an nRF52840 module), but I got an idea to look after a similar keyboard with different layout and move the buttons to that.

In Hungary we use a lot weird accents, so the US keyboard is not suitable for us. Luckily I was able to buy a Spanish keyboard for 15 bucks which arrived safe before the christmas rush.

Aaaand the shift is functioning on this particular one!

Stay tuned!