>>>I KNOW what the problem is. Dissimilar metals and or corrosion.
Al wire is now banned in most housing applications. Why? Because the connections degrade and can actually heat up to the point where they can cause a fire.<<<
YES! This is a fire waiting to happen - the failed circuit is just a warning sign. Fires can occur with Aluminum wiring with no warning. Please read this CPSC info. There is an approved method of adding copper pigtails.
http://www.cpsc.gov/CPSCPUB/PUBS/516.pdf