NE 6D 73 - help! Ab3 not responding correctly to dynamic

[kimuz]

Hello,

i just sold my NE 6D 73 (waterfall keys) and i never noticed any issues with the keybed when playing piano part.
now the buyer has just received the keyboard and wrote me that he feels a weird dynamic response in the Ab3 key (only that one), saying that is not responding as it should.
further is complaining that on the bottom, two screws are white and not black and this means someone have opened the keyboard before.

i bought it from a shop as an ex-demo ones, so not sure what happened before, but

- are all screw actually black ?
- what i can tell the buyer to check for the Ab3 issue ?

thanks for any hints

[Elias]

I don't have an explanation for the screws, but the problematic key is probably to do with dirty contacts. There are loads of threads and instructional videos on how to fix them.

[kimuz]

Thanks will search for some tutorial