The coin door noise is due to the machine trying to reset. It is trying to reset because it never sees the 1000's reel get to zero. Check your switches on the 1000 reel. If don't see anything, with power off, reset all of the score reels to zero, then power on and start a game.

If the 1000s reel starts moving, the machine is not seeing it zero - you need to trace and see why.

I just got a Space Time and fixed it up. The button you have circled is the collect tunnel and if held down it will repeatedly score the tunnel value and releases the gates. If I hold a 1000 score switch it energizes the 1000 score reel and will stay frozen until I release the switch. So if you are continuously scoring there is something else going on, maybe something is causing the score motor to continuously run as well as the 1000 switch? Often that is a score reel switch but could be many other causes. Unplug the coin door and see if stops. You can also unplug playfield and see if everything stops. Look on the schematic and put paper in every switch that activates score motor and 1000 points.
On my machines I unsolder the coin door relay and affix the rod so it will always accept coins as a way to save power and stop humming.
Good luck. I put colored LED lights in the tunnel and it looks fantastic. I will be posting the fixes and results on Youtube tomorrow.

EDIT: I just looked a schematic and the coin chute switches are required for score motor to work properly, so unplugging coin door connector does not give that much diagnostic help.

Agree with SkidDave - you have a 1000 point switch stuck closed. To verify, see if your 1000 point relay is closes when you start a game.

I think the switches are the tunnel unit disc, left and right out rollovers, and right alley 1, 2, & 3 rollovers.