Hey there @mighty_ganesh! Welcome back to the community! Changes in GPU drivers or updates to the engine can cause shader recompilation to be necessary. So if this was between a couple months, it’s possible your GPU drivers or a hotfix to the engine had occurred in the meantime.
As a note, cached data of all types in most software engineering disciplines tends to have a time frame where it is set to be invalidated anyway. I don’t believe that is what’s occurring here, but without a deep dive into the source, it’s just conjecture.