Official Answer
Answer
A sudden load drop in a nested spring usually indicates 'Wave Misalignment' or 'Shifting.' In a nested spring, the waves of each turn must stay perfectly aligned to act as a single unit. If the spring is not properly guided by a bore or shaft, the turns can shift relative to each other, effectively changing the spring from a 'parallel' system to a 'series' system, which reduces the spring rate by a factor of $n^2$. Another possibility is 'Coil Overlap' where one turn slides over another due to excessive radial clearance. Ensuring tight tolerances on the piloting diameter is the primary solution to prevent this instability.
