serpentine head caps

Hi there--

I'm having a strange issue where sometimes my head caps fail to render/show up. I'm trying to use the flat horiz-arrow headcap. This happens about 1 out of 10 times. Not sure why-- but it's driving me nuts. Sometimes if i go into serpentine and set headcap to none, and then back to flat horiz arrow headcap, it'll show up again. But if i jump to another comp there's a good chance it disappears again.

Any ideas on a fix?

I'm using Serpentine 2.0.0 on a mac running AEP cs5