Well, here we go, some pics and description of what happened and what to do when your nightstalker starts to lose velocity.

Step 1: either use up all of the airsource or press firmly forward against the cocking lever, point in a safe direction, pull trigger and easily allow the cocking lever to return to uncocked position, then remove the airsource cover on rear of gun.



Step 2: using appropriate allen wrench, remove the cocking lever.




Step 3: laying gun on right side, remove all screws from left side of receiver (there aren't any on the right)



Step 4: starting at the bottom most portion of the grip frame, begin to pry apart easily.



Step 5: once pried apart, acting like the scope rail is a hinge, rotate the receiver upwards until clear then set aside.



Step 6: grasping the rear end of the valve tube, or the airsource if still attatched, raise slightly and rotate the tube counter clockwise and up out of the receiver. Make sure you clear the trigger sears of the tube before pulling out!!



At this point, slide the port/magazine pressure point toward the foreward part of the tube and look at the valve port/ o-ring and make sure the port hole is centered. In this pic, it has turned due to the tightening of the airsource cannister and the set screws not holding.



Also notice the space between the end of the valve tube and the airsource adapter.