Ok let's break it down gun by gun.
On the AT85:
It sounds like you are saying that the forward retainer on the piston shaft is missing and the coupling is loose. The bolt does not have an 'arm', the shaft that connects to the bolt is the piston shaft and the part that goes into the track on the right side is the coupling.
Are you using an adjustable regulator on your supply bottle? If you are slowing increasing the pressure supplied to the gun you will have air leak out the valve when the hammer is separate from the bolt. The hammer spring is pressing the hammer back and this opens the main valve. Without about 300+psi behind the valve it will be pressed open by the relaxed spring. This is also a good way to destroy guide plates. As you are slowing adding air pressure the system tries to cycle but without enough pressure to compress the hammer spring it can begin to pull the cog backwards and this pulls the cog pin down and back, as it reaches the point that the spring has more force the bolt starts to go forward again and this causes the cog pin to move up which drags or bends the leaf spring. Long explanation short, don't turn the air up as its' connected, instead connect it with at least 650+psi to start.
Since it sounds like you have the housing out look at the retainer. It is the stamped metal piece holding the piston and cycle valve in place. There should be a 'tab' that stops the forward travel of the cycle valve spool. On the older retainers this tab tended to fatigue and snap off. If it is not there your cycle valve spool can over-travel and prevent the gun from cycling.
Another thing to check with the housing out is the placement of the timing collar. This is the collar on the lower section of the piston shaft. It needs to be pressed firmly against the lower section of the 'stack' on the shaft. If this is loose it will trip the rocker before the bolt and hammer have connected and prevent the gun from firing after the first shot, sometimes it will prevent the first shot as well.
Go over those and if possible reference the owner's manual for proper part identification. It always makes things easier if we're both talking about the same whatitz or thing-a-m-bob.
