When research started into fuels suitable for internal combustion engines a peculiar new phenomenon was discovered. Researchers noticed that when engines were being run at certain RPS (revolutions per minute) the engine would suddenly fail, often in spectacular and unpredictable ways. This came to be referred to as Critical Instability.
Energy release and the aether
Normally it is not possible to manipulate the aether mechanically, but as with almost everything there is an exception and in this case it's critical instability. What happens is that when energy is released it has a nigh on immeasurable effect on the surrounding aether. The effect is so small that even at extremely high levels of energy released (like when detonating an atomic bomb) the effect on the aether is still negligible.
One single instance of energy release does not have any real effect on the aether. However, the same does not apply to the same amount of energy released repeatedly at high constant rate for a period of time. The repeated release of energy can under some circumstances cause resonance in the ather, leading to the effect on the aether becoming increasingly more noticable. Once the aether has started to resonate it very quickly spirals out of control and in effect the aether channels and weaves itself.
The frequencies during which the aether will resonate like this are highly dependent on the component releasing the energy. Scientists and researchers are talking about Criticial Instability Frequency (CIF) as a material property. As a matter of tradition CIF is usually measured in RPM rather then Herz. This is a nod to how the property was discovered and where it still matters most - the research of fuel for internal combustion engines.
The basic effect of critical instability is that when the aether resonates at a high enough frequency for long enough it will start to channel and weave itself. This self weaving has so far proven to be very unpredictable and completely uncontrolable. The only thing that can be taken for granted is that the effect will halt the process that generates the energy release, effectively preventing the aether from further spontaneous channeling and weaving.
Anecdotal evidence also has that the more expensive the equipment involved is, the more violent and destructive the consequence of reaching critical instability will be. This has not been proven conclusively, but it adheres to Murhpy's Law.
That critical instability is a significant issue when researching fuels for internal combustion engines has already been noted. However, critical instability needs to be considered under other circumstances as well. Most notably it's a factor for automatic rifles. The issue is of less significance for firearms though. The rate of fire is often constant and the number of shots that can be fired before needing to reload is known.
A less obvious area where critical resonance may be a factor is high speed data communication. It is not yet conclusively proven, but there are several hints that critical instability may be a limiting factor when it comes to sending data packets.