An RF oscillator should be electrically and mechanically stable. This is to ensure that the oscillator does NOT:

The fundamental purpose of an RF oscillator is to generate a specific, steady radio frequency. To maintain this exact frequency over time, the oscillator must be protected from environmental changes. Physical vibrations (mechanical instability) or fluctuations in temperature and voltage (electrical instability) can cause the generated frequency to wander. When an oscillator's frequency wanders, it is called 'drift.' A drifting signal forces the receiving station to constantly retune their radio to follow your transmission, which makes communication difficult and can cause you to accidentally transmit outside of your permitted band. Distractors like key clicks or overmodulation are issues related to the transmitter's keying circuitry and audio modulation stages, respectively, not the core stability of the oscillator.