I don't myself especially without more info. Is it getting out of the mag and jamming or stuck in the mag.
I'd be looking closely at the follower, and maybe the feed lips. I know tweeking the feed lips can make a huge difference but not specifically to the last round. But maybe so.
I sense I'm not helping but I'm pondering.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."