What is usually a sign of a failing Electronic Speed Controller (ESC)?

A delayed response from motor inputs is a classic indicator of a failing Electronic Speed Controller (ESC). The ESC is responsible for regulating the power supplied to the motor based on the pilot's commands. When it begins to fail, it may not process these commands promptly, leading to noticeable lag in the motor's reaction to inputs on the control sticks. This delayed response can significantly impact the overall performance and control of the drone or aircraft, making it handle poorly or feel unresponsive.

While consistent motor speed indicates that the ESC is functioning correctly, unusual noises from the battery can suggest other issues unrelated to the ESC itself, such as battery damage or discharge problems. Similarly, a battery over-discharge warning pertains more to the power source's condition than the ESC's operational status. Thus, the delayed response from motor inputs acts as a clear symptom of potential ESC failure, indicating that it may need attention or replacement.