I've got the sunfish one ... OEM in my Minifish.
It lets water
in and out very well. Mostly in....
No signs of damage to the device. The ball moves freely. It just never seats to block water
from coming in.
I guess you're supposed to lean the boat
over so much that water is sloshing in over the top and you don't notice that the drain is leaking into the boat
That's the way I used to sail Sunfish... mostly leaned over about 60 deg with one foot on the daggerboard. The little footwell was always full of water.