Fundamental phase jumps in oscillators?

Is there a fundamental and inevitable process that causes occasional phase jumps in any oscillator? Can such jumps be explained, for example as small randomly occurring frequency excursions? What is the occurrence rate of such jumps, and what is the maximum rate of phase change and frequency? Is there a dependency on, for example the energy density in the resonator? Is there any way in such a process could be controlled and minimised?