Scope, gun, or me?

Hey folks. This is my first post, and I just joined the group. I have been airgunning for years, somewhere in excess of 20. I'm here today looking for a little insight. After much modification and accurazing a magnum springer, I have noticed that that my 'group' is covering about 1.5" at 21 yards. It's shooting pretty much a circle in 5 or 6 shots. This group is actually a group of 5 or 6 mini groups that are extremely tight with clover leaves and all but 1-holers. Like the poa is changing from shot to shot. By my reckoning, if it was operator error, it would be tight groups with flyers. If it was the gun, it would be all over the place without any consistency at all. That leaves the scope. The scope on it is a subpar scope that is 12+ years old and I highly doubt that it was ever meant to be put on a springer. So here's my question; what would ya'll suspect based on ya'lls experience. Take out the age and quality of the scope, and just base this situation on operator, gun, scope, and how the groups are patterning in a circle. I also hear a rattle from the eye piece end. If I knew how to post a pic, I would. The pattern is random in which group it will shoot from 1 shoot to the next, but it consistently shoots mini groups in the actually group. I shot 99 rounds 2 days ago, shooting 12-15 round sets each time. It would shoot vertical high, vertical low, horizontal left, vertical high, horizontal left, horizontal right, vertical high, horizontal left, vertical low, vertical high, vertical low, horizontal take a wild guess, etc.... These are all inside of 0.348" down to all but 1-holers.
 
What you describe could well be down to a loose scope 'element' or lens. With the age of the scope (you are using) it's possible that a lens has become detached from its carrier - it's obviously not the reticle element, as I'm sure you would see that effect as it happened. The loose lens could actually be rotating somewhat upon recoil.