The only possible explanation for black footage at the end of your sequence is that there is a clip somewhere down the line that you've missed. I can't think of anything else that could possibly cause this.
No, as I already stated, there is no extra clip way far out. Hitting the 'end' button would have found that. Instead, the problem was that little gray marker. That marker was strangely way far out. I never had that happen before. You'd think that it would go to the end of the last clip automatically.
So now, problem solved.
Was that "little gray marker" the end of the WAB (Work Area Bar)?
If so, it was probably set to an older Duration, that was tightened up, as you edited, and just stayed out there. In the WAB, there is a little "box" right in the middle. Dbl-click on that, to automatically reset the WAB to just the Clips on the Timeline.
You'd think that it would go to the end of the last clip automatically.
Ah, that never occurred to me. It does by default shrink and expand automatically to fit the duration of your sequence, but only so long as you never adjust it manually. Once you adjust it manually, it will never go back to adjusting automatically.
Not a bug, but certainly a design flaw in my view.