I have noticed from my last rip to the range a good number of cased I picked up had bent case mouths on 1 side. The brass was ejecting forward and landing in soft clay/dirt. I was firing from an WRC REPR AR-10 with a SIG supressor attached. I reload with a single stage Lee press and Lee dies and apply a crimp to all rounds. The openings look "D shaped" and not round. This isn't happening with all brass maybe about 40% of what I am shooting.

The cases are spinning around and striking the receiver. A common problem.
Remove the ejector and reshape the tip to just touch the case at the outside of the primer pocket,not at the outside of the case head. This will stop the problem. I've done it to many rifle.

Welcome to AR!

The cases ARs eject often have dented mouths.

To me, the "why" has been a "so what" question.

I've reloaded tons of such cases (many, I believe, scavenged from SAWs) and I just check them for splits or other defects that might compromise safety.

If they pass that filter, I resize them, trim them, prime them, load them and shoot them.

But am I missing something here, something that would affect accuracy or safety?

they will straighten out in the first half inch of resizing.
be glad it's the mouth and not right at the body shoulder junction like a BAR will do to 0-6 cases.

I think I figured out the issue, since this was the first run with the can on the gun, I neglected to turn the gas port to the "S" position. The result, I believe, could have been over gassing, causing excessive force on the piston rod, bolt carrier etc.