Lots of good information has been given.
I would be very hesitant to load in the dummy rounds randomly without someone to confirm that the misfire is a dummy and not a hang fire, or in the least, practice proper ammo problem discipline that is printed on every ammo package. I am never surprised when I ask in my handgun class what the proper procedure should your gun not fire and when I get a part answer, the prudent time of the pause, keeping muzzle in safe direction is very seldom offered.
Also, I would advise you, if you haven't already, have someone else that is a confident good shot test fire you rifle. If you are positive that your firearm/ammunition is and accurate you won't have that question troubling you.
And, have you checked yourself for eye dominance recently? This can change,
And did anyone say, Dry Fire yet?
Best to you.