I had Grados for many years...cartridges, headphones....they all need lots of time before they dance. Be patient
+1...I was a Grado dealer for many years and have owned a ton of their stuff. I probably have at least a dozen different Grado cartridges in the corral right now.
IMHO, the regular Grado carts need about 40-50 hours and the wood body carts need about 80-100 of break/burn-in. YMMV.