It's most likely you've got some stray frames of video beyond the true end of your movie.
Press the \ key on your keyboard (above the Enter/Return key) to view your entire project's timeline. It's likely your view will show a timeline that goes beyond the true end of your movie. Click and drag across all of the tracks beyond the end of your movie to snag these stray frames and then press Delete on your keyboard. Press the \ key again and the timeline should snap to the actual length of your movie.
Since you have at the onset done what is being suggested, consider the following
1. Expanded the Timeline to max with the -+ slider above the Timeline.
2. Press the End key of the computer keyboard.
3. Wherever the Timeline Indicator stops, open and inspect all tracks that are created in the Timeline.
Look for very thin vertical black lines scattered about, look for whole clips that may have been pushed out of the way and forgotten about, look for fragments of clips that might be slightly larger than the thin vertical black line type.
4. Repeat the End key routine until the Timeline Indicator stops at the end of the intended Timeline content.
We will be watching for your progress as your schedule permits.
Until I saw your response, I, too was pulling my hair. I couldn't see anything until I used the / stroke. Thank you!