When you say it catches on the return, do you literally mean the bolt is slow to spring back, or do you mean it just recharges slowly?
If the distance from the center of the rear field strip screw to the bolt spring seat inside the body is different (it can vary significantly even from one AGD body to another), you may need to tune the Level 10 to that particular body. Perhaps the distance is longer, so you need a longer spring than the gold one you indicated you are using. Are you using the largest carrier that doesn't leak? If not, this hypothesis holds more water, as bolt stick with a weak spring (for the longer distance anyway) is more likely.
Are you using a ULT? That may need to be tuned for a specific body as well. Slowly add shims to see if that helps.
I haven't done a pneumag (yet). Is the ULT required to help it cycle at a lower lpr setting?
Last of the Salzburg Clan