New 50th Anniversary 10/22 functioned fine when first briefly tested. Now when I fire it, the next round chambers, the bolt seats, but won't fire because the hammer has not been cocked. Pull the bolt back, ejecting the round and the next shot fires just fine. Total rounds fired is probably less than 40. I have cleaned the chamber, but have not disassembled the trigger mechanism. Also notice that the unfired, manually ejected cartridge has a slight dent on it like the firing pin had touched it. ??? Any ideas?