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HiCustomer You are not on the wrong path. The troubleshooting steps you have taken so far are good steps to take. You will need to continue opening wall boxes on the affected circuit, and inspecting the wires inside. This sounds like a direct short, where the ground wire or a neutral wire is touching the hot wire or the hot screw on the side of an outlet. Before you go to the trouble of opening more wall boxes, make sure you have unplugged everything from all of the outlets on the affected circuit. There could be a faulty item plugged in that is causing this problem.
These types of problems can be frustrating to find, especially if there are a lot of outlets and lights on the affected circuit. You may have to open a lot of wall boxes. Also, it wouldn't be a bad idea to open your electrical panel, if you are comfortable doing so. Once you get it open, I recommend trying to tighten every wire in the panel. This includes the wires on the breakers (with the breakers turned OFF, for safety), as well as the wires on the ground/neutral bars.
After performing these troubleshooting steps, please post back here if you don't get the problem resolved. I will continue to work with you on it until we get it fixed, or exhaust all means of remote troubleshooting. Thank you.