Please help w/ A5 low fps, auto-ing, etc

Two requests: First, I'll give you what happened today and maybe you've got an idea of what's wrong. Second, I'm trying to understand how the marker functions. Please tell me if i'm right / what I'm not getting.

I picked up a used A5 two weeks ago and put a few bags of paint through it testing it out. It worked fine.

I got to the field this morning, took off the rear plate/sling swivel and put a drop or two of (paintball) oil on the rear bolt. I also put a drop or two of oil in the ASA and fired it to move it through the gun.  I took the gun to chrono and immediately started having problems:

I could not get the gun to shoot much more than 200fps. Turned the velocity screw out so far that the gun would just stutter, but never got above 215fps. Turn it in, and it would go down to 170fps.

Here's the big problem: If I got any sort of good high rate of fire going (esp with the E-grip) the gun would go to full-auto on it's own and would continue until I shut off the air with the remote. I disassembled it at the end of the day and found that the rear bolt o-ring was stiff and worn-out. Hopefully this was the issue.

So maybe if I understand how the gun operates I can troubleshoot it.Tell me if this is right?

1.The trigger trips the sear, which releases the rear bolt.

2. The rear spring pushes the rear bolt into the valve, striking the valve plunger. The front bolt, linked to the rear bolt, has moved forward and moved the ball off the detent.

3. The valve opens, allows air down the side channels, around the tombstone, and into the front of the power tube, firing the ball.

But what makes the action cycle back, i.e. what forces the rear bolt back to catch on the sear? Does air escape around the valve plunger when it is depressed to force the bolt back?

Gotcha.

Clarification: Edges on the sear in the mech grip and in the e-grip are sharp and fresh, as is the edge on the rear bolt/hammer.

I believe I have some sort of low pressure: not enough blowback to push the rear bold back to reset the sear, therefore the gun just full-autos. Which o-rings would affect this? The valve-to-tombstone o-ring? The rear valve o-ring? The rear bolt o-ring?  All or any of the above?

I don't understand why the gun would keep full-autoing when there isn't enough air. It should eventually just stop because less and less Co2 is being blown back (resulting in the gun failing to cock) and eventually the bolt is not pushed back far enough to gain the momentum to activate the valve plunger.

When it goes full-auto, it will cycle no less than 200 times before stopping... I only know this because it burned through a full hopper of paint twice.

This morning, I went ahead and mounted the tank directly on the bottom line and gave it a shot. Same story... full auto until I unscrewed the bottle.

I'm grasping at straws too.

Now I'm not sure my e-grip trigger group is assembled correctly. I took it apart, and found that it has the slider installed (part 98-18), as well as an oval-pivot-hole sear (part 02-35) instead of the sear shown in the e-grip diagram (part TA01135). So I took out the slider and put in the e-grip sear, as shown in the e-grip diagram.

Before I did this, I could use my marker with the e-grip turned off... it just worked like a normal mech grip. Now the trigger will not trip the sear unless the e-grip is on. This seems like a serious un-improvement... as my battery could go dead in the  middle of a game and I'd be screwed.

Um, whiskey tango??