If it were mine I would first strip out the cylinder and back block.
Hold cylinder up to the light and see if it is a clear straight path out the silencer.
Check silencer for clipping.
Push a pellet up breech and gently push through bore to see if any tightspots , see if it falls right out the crown end, indicating if there is a problem with barrel choke.
Next I would change pellets and go for a new tin in a different batch.. sometimes I have had a tin of jsbs enacts that some fit lovely and others in the same tin nearly fall out the breech.. make sure you technique is the same for every shot fired..

How's the trigger? Is the second stage nice and light? Or hard? Could you be pulling the shot?..

If all is fine I would change the scope for one you trust and fit and see. You are trying to eliminate problems.,

I had a hw97 that shot spot on a number of years ago and it turned out to be the mtc scope was not holding zero.. put another on and it was back on target..