I agree with follower and a cause.
Feed lips would effect most rounds.
If it is ONLY the last one or two rounds in the mag then the follower may not be holding them up properly.
In this pic you can see how the follower, the last round, and the next to last round should look.

If the rivet holding the follower is loose it will allow rounds to sag.
When the mag has several rounds the rounds help to align the top one.
When the mag is low on rounds then the follower controls how the rounds sit.
Check the rivet for flop.
