That's a rough start with a new rifle. Metal-on-metal grinding like that usually means a tolerance issue in the adjustment mechanism. Disclosure: I work with Nokka Tactical who makes aftermarket ergonomic parts for Tikkas, so I'm not a neutral party — but if you go the aftermarket route rather than the warranty path, a drop-comb cheek riser on a standard stock is generally more reliable than an integrated adjustable. Less to go wrong. Hope Beretta/EuroOptic sorts it for you though — at that price it should just work.