The first question is: Is the revolver still in original stock condition, or has someone played with the springs? If the answer is, "yes it is," the next thing to check is cylinder end shake (which means back & forth movement of the cylinder as opposed to rotational movement). If there is end shake it probably needs to see a gunsmith, or better yet - go back to the factory.
The probable reason for the mis-fires or no-fires is because the hammer stroke in double-action is shorter then it is in single-action, so in D.A. the firing pin gets a lesser whack from the hammer. A stronger mainspring may cure the problem, but you will hate the trigger pull.
You might try a change in ammunition and see if a different brand works better.
Last but not least, since they will pay the shipping costs, I'd consider sending it back to the factory for a complete going-over under warrantee. At that time any and all issues should be addressed.
