Why Microphonics are frequency or amplitude variations caused by mechanical vibration or shock reaching the oscillator, where movement of components, leads, or the tuned circuit slightly changes capacitance or inductance. The cure is mechanical, not electrical: shock-mount or isolate the oscillator board from the chassis and enclosure, keep leads short and rigid, and secure components so nothing can vibrate. Potting or clamping critical parts works on the same principle.
Watch out NP0 (C0G) capacitors are the standard fix for thermal drift, since they have near-zero temperature coefficient, but they do nothing about vibration; cleaning up power supply noise reduces hum and phase noise, not microphonics.
Microphonic = mechanical. A mechanical problem needs a mechanical fix: isolate and mount rigidly.