Okay, here are some pics of the 2 buttplate inserts.
In this pic I oriented inserts front/back with buttplates beside them for comparison. Also, the one on the left is right side up (cross-shaped post pointing up, as if ready to position under the bottom of the mag spring), and the one on the right is upside down (you can see the round post to fit inside the buttplate hole).
Notice that each has a narrower front end profile, to conform to the rounded front shape of the mag body (and flat rear for flat rear wall of mag body).
Also, note that the front lip is visible on the left insert. More on that in a moment.
Here's a pic with the steel insert located to the left of the plastic ones (oriented right side up, which means the buttplate post is on the bottom).
Here's a pic of the plastic (top) and steel (bottom) inserts, oriented so the front of both is on the left. Note the front lip that is intended to fit inside the mag body (and to keep the front edge of the insert from slipping forward, becoming caught between the bottom of the mag and the buttplate). Note how the plastic insert has a less obvious front lip, but that it's still there. Make sure the mag is assembled so the lip of either style of insert is wholly inside the bottom of the mag body.
Okay, it's not unusual for the top round to be displaced slightly forward under the slide's pick up rail after a round has been stripped and chambered. Especially as mag springs start to weaken.
In earlier .45 mag body designs it was more common to happen easily, before the wide pressed indentations were added to each side of the mag lips. Some older mags even had some small and short "cut" indentations toward the rear of the sides (similar to .40 mags) that put pressure against the case rims to help try and prevent forward displacement, but the longer/taller "pressed" lip indentations were the latest revision for the .45 mags (except for the CS45 mags, and some 6rd 945 mags, if I remember right, which had secondary indentations of a more vertical shape).
This top round displacement after loading can also be observed in 9/.40 mags, BTW. Sometimes the top round might be sticking so far forward (especially in a single stack 9mm mag loaded with long 147gr rounds) that the bullet nose catches on the top of the mag well, and pulls the round out of the mag as the mag is pulled out of the gun.
It's not common to hear of it actually becoming a problem during live-fire, though. The recoil forces and friction with the bottom of the slide usually bounce/push the top round back within the mag lips as the slide slams to the rear, so the top round is in position to be stripped and fed during cycling.
Here are some pics of a disassembled 7rd mag (4513TSW/457) with the parts oriented for direction (top/bottom & front/rear). An overall pic and one each for the top and bottom, to show the follower and insert (steel, in this case). Note in the follower pic you can see the front small loop sticking toward the front, and the rear of the top coil visible in the follower cutout in the sides.
It would become pretty obvious, by comparison, if the spring were upside down and/or backwards.
Hope this helps.
