Yes, all the things you mention could be the cause. It also could be a bad breaker. More than likely it is a problem with a connection as said above. If you can isolate/find the breaker that feeds that particular circuit you can test for proper voltage. If it's good at the panel you will need to find out where the cable goes from the panel to the problem area. Don't open everything up. Try to use some common sense and see if you can find out where the circuit starts. Then one at a time check all the devices until you find it. Or call an electrician. Good luck.