"Tominco"Sounds like you may have a possible clipping issue. Sometimes the magazine doesn't line up perfectly as it should with everything else. When you push the pellet forward, it may be slicing off an edge. Look for any shavings in your magazine, on your shooting bench, and anywhere else.
Also, check your O-rings with a very bright light and magnifying glass. It's not always apparent that an O-ring is damaged.
Are you shooting JSB's? Smooth twist barrels really like JSB's.
Also, shoot with the end cap off the LDC/shroud and see if that makes an accuracy difference. Be advised, it will shoot MUCH louder. But, it's just an experiment to see if you're clipping the end cap.
Yes, your power is off. Check the setscrew behind the power wheel. I think Ernest @Sniperlabyo has a video explaining how to take the slack out of this. However, you seem to be way off the mark. So, I'd consider calling AoA back again and explaining to them exactly what you have going on in detail. Since they just repaired it and it is still not performing, you may have to have them send it back to themselves.
@Scirroco - I agree with you about cleaning the barrel. But, over an inch at 50 suggests that it's something more than that. A dirty barrel + a clipping issue could add up to an inch at 50 pretty easily.
Tom