Pen tool drawing strange shape in premiere

Hi Everyone

I'm having trouble with the pen tool in premiere. Can you help?

I want to draw a simple straight line with square ends but instead I am getting a line that has a white space in the middle and has one rounded end and one square end as in this screenshot.

I have fill off and stroke on but can't find any way to change the line ends or to get rid of the white space.

Thanks very much for your help!