I've heard of this, but on other assemblies.
You first need to find if there's any abnormalities of straightness between the receiver and barrel.
Run a straight-edge along the centerline of receiver and along the barrel's centerline all way to front sight to help determine any cants off to the right.
Now, knowing if barrel/receiver are straight, you need to determine if front sight is canted off.
Put assembly in vise to hold in a vertical 90* and put a straight-edge along each side of the front sight to see if it's mounting is vertical also. If not you found the problem. Sometimes you can see a sight's cant by visual.
Another source of shooting either right or left, is remove the handguard and check tightness of barrel nut and that it conforms to proper torque. I've heard of looseness in this area before from PSA.
If all straightness checks and barrel nut check are good, then I would say your UTG sight is bad. It's possible it's an airsoft sight and not a good AR sight. If you want a good sight for not much money, I use Pro Mag on my ARs.
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