I have a CZ 452 trainer and the rifle shoots great. I did put a scope on mine and it will shoot quarter size groups of 10 at 50 yards.
Make sure you don't rest the barrel on the bags. Only rest the stock. Try to get your spot close to the action screws in the bottom.
If you let someone else sight in your rifle, you will probably not have the same sight picture.
Let someone else shoot the rifle for groups but don't adjust anything until you have had a chance to shoot it yourself.
If there is a problem with the gun, an experienced shooter probably won't get decent groups either.
My gun was shifting point of impact almost 3 inches at 50 yards and it would happen between rounds at the range.
Not knowing if it was the scope or the gun, I had the on site gunsmith glass bed the rifle and do a trigger job on it.
I got it back last week and the rifle is shooting really good.
Maybe you are having the same issue with your gun. It might be worth a check.