Originally Posted by Gilly

Under where you thought the adjuster would be (under the "solid" piece) is the hydraulic compensator, this operates like a lifter in a pushrod engine, and it can wear out, just like a lifter can collapse, so can this .
Or there is another possiblity. Between the compensators and the valve stems there is a small cup-shaped spacer, this I have seen flip out from between there somehow and will make alot of lifter-type noises.

Gilly