They come with an anti rust coating that needs to be removed with acetone before use. I can see gray burning on the contact as if there is a poor connection between the two contacts, remove this with a file. I have no picture for say but I can use your first pic as an example. Start by making sure the screws are tight. Then put the file in between the contacts and apply light pressure to close the contacts while filing them flat and clean. The single blade in your pic needs to be bent towards the coil more. You can see that the blade has an arc to it away from the coil, this causes the contacts not to be square and a poor electrical connection. High current thru poor or loose connections means heat. If you were to remove this switch you would see how little contact they are making. Now besides a square contact there also needs to be a certain amount of pressure holding the contacts together, if this is not enough the flipper will get weaker on a long game. The contact pressure is not preadjusted and needs to be set any time you work your flipper mech. Once you set the pressure then you can check the EOS gap by only pushing on the coil plunger. If you do it any other way your gap will be off by the amount of play in the flipper parts. All lot of the time you need to do this 3 or 4 times to get it correct. As you change the gap it might change the contact area or the contact pressure. Once this switch is done you can do the other stacked switches.