Rightmost column of slave board stopped working

[hexed phoenix]

hey there, I have a generic question about pcb troubleshooting, my rightmost column of my slave board (split) stopped working overnight, as far as I can tell nothing has been done to it, my wife was cleaning my office so at most she just dusted the keyboard.

Keyboard is in a full case, so exposure to ESD would be minimal. Everything works apart from slaves rightmost column (del, bksp, apostrophe and shift).

I reseated the switches but no dice.

I am very green when it comes to electronics.

ok I have something, when I test with multimeter set up for 20V AC and I put the ... prongs to one of the soldered points of the PCB and one of the sockets that don't work I get some voltage. If I put it against one of the sockets that workI get 0 voltage.

ok that theory is is invalid, I managed to get other sockets to "pass" voltage as well by touching on different soldering points