Why exactly do arrows ghost?

[Rene_A]

Ive seen many a ghosting arrow on my own pad, and in arcades. Sometimes it just goes away but i never really know how to fix it, what exactly causes it? and how can i prevent it and fix it, on my own TX-2000 and maybe help out the owners of this DDR machine in the area where the arrows ghost ALOT
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bleedingdonkey (9:55:35 PM): HAI
bleedingdonkey (9:55:40 PM): I NOTICED
bleedingdonkey (9:55:43 PM): THAT YOU AAA'D SEVERAL SONGS ON DDR
bleedingdonkey (9:55:47 PM): I AM PROUD OF YOUR ACCOMPLISHMENTS
Rene Aq (9:55:58 PM): OMG WHY THANK YOU SIR

[mtwieg]

most likely one of two things:
1) contact is actually made by accident (panels are too sensitive or some wiring issue)
2)static electricity builds up to the point where current will actually spark between the contacts
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[FirstClass]

Another reason (perhaps less common) is that the foam which holds the arrow up when released has been compressed and refuses to reform properly again therefore the switches are barely making contact.