I have noticed this issue this morning when I exported a clip and accidentally selected 30 fps, when all my source media was 25 fps.
Exporting to a 25 fps video such as DVD PAL was fine, but exporting to DVD NTSC, introduced the white flashes at the start of each clip.
So I would guess that the white frame may be something to do with the frame rate conversion.
I have noticed this issue this morning when I exported a clip and accidentally selected 30 fps, when all my source media was 25 fps.
Exporting to a 25 fps video such as DVD PAL was fine, but exporting to DVD NTSC, introduced the white flashes at the start of each clip.
So I would guess that the white frame may be something to do with the frame rate conversion.