Only with the 7 round you have an issue? Are you loading using the slide stop release or sling shot method.
It could be you have a burr or rough edge on the feed lips of that 7 round mag.
A pencil or a dowel with some fine sand paper can clean up the sharp edges. Spring might be a bit strong and the extra pressure on the rounds pushing up creates a drag. Look over the follower as well. Some have successfully reprofiled and cleaned them up to feed better and sling shot much easier as well.
Some report having issues only with the larger mag, some feel it's related to pressure from the pinky finger on the base plate, not sure there's enough wiggle room for that to happen but it's possible as they have no issued with the 6 rounders.
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."