What would cause the pcv valve to rattle in park and while driving
metal pcv valves transfer the knocking of the engine into audible sounds most plastic pcv valves are quitter but this is normal and not really much you can do about it its just a pressure relief system that allows oil to blow past it in the event pressure gets to high
Or the vacuum hose is bad, causing not enough pressure to hold the valve up while the engine is running.
It's normal.... Some brands of PCV valves make more noise than others. If you are concerned I would replace the valve with one from the dealership. Some after market PCV valves can cause issues.