NOOB Question: Text keeps moving during playback.

Thanks all for letting me join. This is my first day with DaVinci, and I've managed to insert a time code into a video clip.

When I click the playback button, the timer advances like it should, but the text jumps back and forth.

I'm 99% certain the cause is operator error. Has anyone else encountered this, and how did you resolve it?

--Buck