On occasion the internal engineering systems used by the problem solvers may fail due to faulty hardware or software. The latter is usually the result of code changes made by multiple engineers using the same systems. Although most large companies have in house field service personnel it is often more efficient for the problem solvers to analyze in house system failures. For the same reason it is often necessary for the problem solver to identify problems caused by multiple engineers using the same systems for testing and troubleshooting. The latter is a kind of "Physician, heal thyself!" situation.