If you remove the lower link, you should see the cartridge stop "finger" (a small stub) sticking "up" from the inside surface at the front end/edge.
The stop is what is supposed to retain remaining cartridges in the magazine until called for.
Some wear down through use, but new ones sometimes are too low/small because they fall at the very low limit of production tolerances.
I've found it best to repair the existing stop by making it longer/taller.
Some do so via welding a little material on top & dressing down with a file; but I've always just swadged (hammered) mine.
I lay the protrusion on it's side, on a steel block (anvil).
I hit the side (use a steel drift) repeatedly with a HEAVY hammer (measure the original length first, so you'll know when it got longer & by how much).
It's better to make it a bit long, then dress it back down.
The repair consists of extending the "too short" stop by only a few thousandth's of an inch - 1/32" is too much.
If your rifle's lower link is of sintered metal, however, welding would be the way to go.
Here's a pic of a worn sintered link (LH) with a welded/filed repair (RH)