When the gun has an indexing issue it will "dump" air out the mag area (loud Buzzing noise). This is caused by an improper regulator and delivery valve adjustment.
So, if the regulator is set low, and you turn up the delivery valve to a high setting the gun will dump (allowing for more flow than the regulator is set to give). The same can happen if the regulator is set for a high PSI then the delivery valve is set to the lowest value then it can dump. Of course this is my take on it, as I do not have a full understanding of how the valve works.
Once Huben advised on this, I would make sure the delivery valve adjustment is in the midrange setting to work with the regulator. This would be my starting point moving the shot power up and down from there.
I know it sounds confusing, but it is real simple once you play with it. I was first really worried as I got the gun, started shooting and twisting the knobs then it would dump the air! I would then rotate the mag then put it on safe to stop the air, and wonder if I got a lemon. Then my wife gave me bad looks as she is the one who footed the bill for it!
Hopefully by the time you get yours, Huben will have the manual worked out and have some TS charts in it.