Electrical shorts inside a computer are sometimes caused by wires that have lost their protective coating and are making contact with internal components.
Inspect all of the cables inside the computer and if any are found to be frayed, replace them immediately.
Also, be sure to check any other wires inside the computer including twist ties and other wires that might be being used for cable organization. While most of these are now 100% plastic, some are metal and will wear over time.
