First
Next, the "wheels" are more commonly known as "reels" - like you'd see on a movie projector. (Remember those?
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Is there any particular problem where you need to see it running with the door open?
I'm definitely not a Sigma expert but very likely there's optic circuits that are "cut" when the door is open. Obviously these are needed for when the machines were in casinos. They can be bypassed easily thought if you really don't want them in use. Post a photo of your machine and one of the side where the other switches are. In some cases, it's just easier to replace those with push button stitches or toggle switches. Or, just find a replacement key switch.
I'll PM a more experienced member and he should chime in with more (and perhaps better) information.