Text filters doesn't work in random parts of the video and image in timeline

I put a black image in the playlist, and stretch it long, I add text filters, and I separated a lot because I need to add subtitles, but some of the parts the text just disappeared. It should appear, but it doesn’t, And I need to delete that part, and then reput that black background to timeline, and add subtitles filter again. That’s annoying.