Sounds *exactly* like the effect noticed on Apple computers with aluminium cases and non-earthed power supplies. If earthed, the tingling disappears. So it seems very unlikely to be a mechanical phenomenon.
I'd bet that the earth connection in the switch box isn't connected there or at the other end of the cable and all this is, is just Capactive leakage..
Yup, I have noted it on metal chassis equipment in the past... You can normally sense it on some touch dimmers.
Some of the Apple power supplies are earthed when used with a cable but not when plugged directly in. (Hmm, think it is that way round...) So simply by using/not using the cable you can switch the tingle on and off.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.