So, I'm looking to understand how this particular problem occurred.  After a range session, I noticed the bolt catch on this lower was rattling loose with the bolt closed.  It would still catch the bolt on the last round of a mag, but wasn't under any spring tension in the closed position.  I removed the roll pin, and found the lower edge of the bolt catch plunger hole rolled/peened into the plunger bore, effectively trapping the plunger inside the lower.  I was able hold the plunger all the way down, and file off the peened edge to free the plunger.

My question is why did this happen?  It looks like the bolt catch pounded the edge of the hole enough to displace material, but why?  Lower receiver problem?  Bolt catch problem?  User error?  I've contacted the manufacturers of both the lower and the bolt catch, but haven't gotten much input on how this could have happened.

I appeal to the wisdom of the ar15 collective; whaddya think?

Was it just a standard style bolt catch? May have just been a high piece around the edge of the hole in the lower when machined that did not get de burred. I would probably just clean off the edge, check the hole size with a drill bit, and put it back together.

Bolt catch was not the typical milspec, but an upgraded type from a reputable manufacturer.  Was in contact with them, though they dont think it was caused by the catch, they did send me another. 
The issue now is, the bottom of the catch no longer contacts the receiver, but rolls into the bolt catch bore, which allows the bolt catch to pivot beyond normal range.

Lower went back to Aero, they evaluated it, and were gracious enough to replace it, but couldn't give me a good explanation for the cause.
I dont want this to happen again, so im trying to figure out the cause.  I've never had an issue with my other rifles, and was hoping someone may have seen this before.

Ok, like I said, the lower receiver is being replaced, but if I see it again, it won't cause any functional issues?

This poster answered this for you perfectly. A tight fit between lowers and the bolt catch plunger is common. I've seen it so many times that I check for it when assembling a lower.

It almost needs to be kind of tight.  SLOP IN that area can cause all kinds of funny wear issues.

Explain your idea of wear at this point. I've never seen a bolt catch plunger have wear issues.

I don't know if I'm understanding this correctly.  Should the bolt catch always ride on the plunger, or is it supposed to bottom out on the lower receiver in the bolt open position?

Sounds to me like the bolt catch spring/plunger hole was drilled too deep. This would let the plunger go too far into the lower, which would in turn allow the bolt catch to make contact with the lower, causing the peening issue you had. This is my guess as to why Aero replaced the lower under warranty and wouldn't disclose why.

That explanation actually makes a lot of sense!  As soon as i read it, it clicked.  Explains all of my observations.

The drawings allow the hole to be deeper than the length of the pin. The catch hits the lower. I think I would look more at the shape and angle of a catch compared to a GI one near the bottom and where it contacts the lower. I googled pics of some catches. One catch pic I noticed looked rounded at the area that contacts the lower.
Would more force be exerted against the lower where the catch contacts it because of leverage by a long lever if it was dropped on that side? Seen some guns thrown in the dump boxes at matches pretty hard.

So, if the bolt catch is supposed to bottom against the receiver, for whatever reason, this particular setup did not have sufficient surface area.  Pic below shows the backside of the bolt catch I removed; note the witness marks along the bottom edge.  What I can't really figure is, once I filed off the peened edge in the lower, both this bolt catch and a milspec bolt catch roll into the bore, and don't contact the lower receiver until it's far enough depressed to contact the sides of the bore.  If the milspec one contacts the lower the same way the "enhanced" one does, I would suspect a dimensional problem with the lower.  Unless the previous poster is correct, and the bore is deeper than it should be.  I suppose stacked tolerances could explain it too.  In any event, I've got a new bolt catch and a new lower, and I'm going to see what happens.

http://i1079.photobucket.com/albums/w509/sluetters762/3_zpssfjm7pug.jpg

Looks like the manufacturer took care of it. Anything else I could add would just be a WAG.

Of course the hole is deeper than the length of the plunger. Its under spring tension and needs to move freely in and out. All of the bolt catches I've studied go into the bore and do not contact the receiver. I'll stand by my assertion that the plunger bore was drilled to the wrong depth, hence the reason the manufacturer replaced the receiver and wouldn't say why.

It is easy to see where the catch hits at the bottom. Just put one in a lower with a correct size punch through the lower and catch. Rotate the catch up till it stops and hold it in place. When you slide the punch out you will have to slide the catch up to get the bottom of it to drop into the detent hole.

That's fine, but remember that the bolt catch only rotates the distance it's pushed up by the magazine follower. You're pushing it much further by utilizing your test.

There is constant spring pressure on the catch.
If Aero elected to replace the lower then likely something was off.