Model M, 8 keys only respond to hard taps

[metamorphosis]

The keys are in different places across the keyboard, and haven't changed before/after with a bolt mod.
The springs and levers all got shifted around so there's no chance it's faulty springs/levers.
Lastly, there's one key which won't respond to even hard taps.

I thought about putting tiny amounts of blu-tack underneath the membrane at the faulty keys, but thought I would get opinions here first.
BTW thanks for all the advice I've absorbed through the various posts here on bolt-modding - it helped.
M

[E TwentyNine]

What specific keys work?

[metamorphosis]

What specific keys work?

All keys work except f5, f12, 0, y, m, ?, right. N doesn't respond but I think I know what causes that.

[E TwentyNine]

Normally I guess you have a trace out or corroded and to reseat the connectors. Not seeing any common traces with those if it's an old style large controller.  If it's the later style with the small controller over the numpad, I don't know if the matrix is different on those and you have a bad trace or connection.

[metamorphosis]

Normally I guess you have a trace out or corroded and to reseat the connectors. Not seeing any common traces with those if it's an old style large controller.  If it's the later style with the small controller over the numpad, I don't know if the matrix is different on those and you have a bad trace or connection.

If it were a bad or corroded trace, wouldn't tapping the key harder have no effect?