Hi thanks for the question.
When you leave the door open at half mast it wont close . Or is it the bottom of the door that wont close.
At the door hinge pin at the bottom does it look like a plastic broken piece.
Its part of the bottom hinge If its worn it will do that to the door.
This is the piece that could be broken and another one.you can see the parts bend down and look at the bottom pin.