After cleaning contacts I use metho and a toothbrush to remove any remaining dirt. Be very careful to make sure that all the metho dries thoroughly otherwise you can set the machine on fire.

You need to make sure that every contact is correctly adjusted.

Try starting a game with the playfield up and looking inside the cabinet, best if it's a little dark too.  Look for any obvious sparks or arching between contacts, that will indicate an incorrectly adjusted contact.

Good luck.

Post your location someone might be nearby to assist you if required later.