I recently had a similar problem with my T460s, where most of the keys of the middle row were not working. Specifically it was a,s,d,f,j,k,l whereas g and were working. I swapped the keyboard (now it seems to be working) and when I disassembled the notebook, I discovered that obviously one screw coming from the underside (which fixes the mainboard in place) is obstructing the cable of the keyboard and left already quite some mark there. This seems to be obviously the reason for the not working keys.