Hatsan has a great return policy. They will get you a shipping label and within two week get you a new one, if it is still under a warranty.
If not, I had fixed a cocking issue in a Gladius for under $20. Remove the cheek piece and access panel to see the cycling mechanism. There is a flat metal piece with two elongated hole that broke on mine. I ordered a new one from Hatsan. I bet something broke in there.