Using Vegas 21.0 (build 315) and randomly getting short glitches like these while working with certain MOV files, always at the bottom of frame. The files themselves don't have these problems, but if I render the video while these glitches are displaying they'll appear on the render. Also the glitches seem to be inconsistent; they'll appear on the above frames for a short time, then if I return to that exact frame 5 minutes later it'll show no glitch at all, or the glitch will have moved to elsewhere in the video.
Any ideas?