This isn't carbon buildup under domes and flex must be replaced. They're on AliEx but it's like $40ea. Yikes.
Just...done with sort of root-causing NEX-5T dial freaking out and enter button dying. The bottom side of metal domes were charred and only some of buttons un-responsive unless flex was pressed hard on a bend at the neck to temporarily fix it. Clearly it saw too much current through some of traces and some of conductive ink lines severed itself.
ハリオすげーの出してきたなw https://www.kaldi.co.jp/ec/pro/disp/1/4977642031371