While pushing down with the stick/ruler, make sure you are pressing the magazine release in all the way...
It's best to unload the magazine before pushing the follower down...
I suppose it is possible for the mag button to come loose and jam things up...There's nothing else that sticks out/in to jam the mag (if release is pressed in)...
You could always try pressing the mag release in while prying down on a base knob with a small screwdriver...