First of all:
Don't fret. Most likely not anything that can't easily be fixed.
1 - you are very possibly hitting the release. The grip is small and "weird" until you get used to it. Some determine that they never can keep their hands off the release in their best grip and choose to file/sand down the release button making it harder to hit. Tape around it so you don't muck up the grip WHEN you slip and go slow, trying often.
2 - Trim, sand, file whatever the TOP of the mag base plate where it sits up against the gun. The extra mold flash sometimes stops the magazine from getting a solid grip in the weapon.
Then and only then, consider ordering an extra mag catch and spring from KT and replacing yours - its not hard. But if you are going to do that consider replacing with a metal catch from Beach on this board.
And finally on a related note - make sure you are pushing in the mag release when you load a mag - just slamming the mag home like you often do with other weapons will tear up the plastic mag catch and cause the same pre-mature release.
-Scott