I have some experience about this matter.  I made some roll
transcriptions years ago, using a pneumatic stack fitted with
contacts similar to those used in organs.

When I listened to the MIDI file music using an electronic instrument,
I found that each note-on event was indeed a sequence of fast note-on
and note-off events, caused by contact bouncing, that the recording
system, that was very fast, had exactly detected and recorded.

I observed the electric signal from the contacts with an oscilloscope
and saw the bouncing.  I had to introduce a short delay using an RC
network [resistor & capacitor] on each contact to solve the problem.

Leonardo Forti
Rome