DNx36 clip render failure

At least once a session, I get a DNx36 clip that fails to render from a closed reel. This is the most recent error I got.

Opening and closing the reel sometimes works, but I sometimes have to quit out of Cortex and re-open it to get the clip to render. Any idea what this might be?

99/2/2016 10:39:00 PM,Error,Cortex//StartEncode(0), Error encountered: Cannot read frame 0 from file J:\CODE_BLACK_DAILIES\EP206\DAY01AM\EP 206\9-2-16\B CAM\B213R2EJ\B213R2EJ\B213C001_160902_R2EJ.mov: Object reference not set to an instance of an object.

Can you export the logs and send them to support@mtifilm.com?