This is a Multi Flexible Body Transient Response Dynamics Finite Element Analysis of a part of the valve train of a BMW M10 engine. this simulation runs the engine at 12000 RPM. clearly seen are the harmonics of the spring. In the simulation below there is no contact so the rocker is sort of glued to the camshaft and valve. But what is clear in this simulation is that a beehive / interference fit double spring is needed to mitigate these oscillations.
The simulation below is with contact AT 12000 RPM. Although the contact algorithm in this simulation leaves much to be desired, one can clearly see that at 12000 RPM the rocker no longer is in contact with the camshaft at all times. Thus more spring force in needed. Doing further simulations "no video's available" it seems that a single spring will not hold the rocker in place much above 6000 RPM.