welcome.
one of my 97s has a rattle, the other doesnt. also, try inserting your mag and see if it rattles. your gun is only good with one shot w/o the mag. it could be the mag break. if you are concerned, remove the grips and see if you can determine what is causing the rattle. if youre not happy with that take it back to your shop or call CZ.
if you want a 1911, buy a 1911. if you want a CZ, buy a CZ. a CZ isnt a 1911 and visa versa. if you want a decocker, why didnt you get the 97 BD?
btw. safety is between the ears. for people that have no issues with lowering the hammer on a live round, it give the operator that chooses to carry it hammer down and one in the pipe.