I agree too. Fix the relay properly with a new blade and contact. Then PLAY the game. The more you play your EM, the better it will run. The Buzzing and Arcing will get better with play. If you go through the game cleaning contacts because they look dirty, you will more than likely end up introducing more problems. The one caveat would be switch adjustment. If slingshot and other score switches are adjusted too closely, the rubber near them and the sling kickers can make those switches "bounce" causing Arcing and erratic scoring. Adjust those switches to have a good clearance from their rubber and good switch contact separation when sitting still.

Dirty playfield is definitely something you want to clean and wax, but dirty switches are usually OK. However, If there is one switch that is way dirtier than those around it, it should get some attention. It is probably out of adjustment and has been arcing a lot. That switch should be cleaned and adjusted.