Operation successful or not?

Has this happened to you and were you able to fix it?
I complete an operation in a scenario, and it disappears from the F1 task list displayed with the F4 HUD.
However when I display the task list without the F4 HUD (the old-style task list with the green checkmarks and red Xs), it is still marked as incomplete.
What causes the difference?
In this particular case, it is a drop operation in the new "Tucker Industrial" scenario for the Colton Northern route.
The track marker is very short (a few feet long). I tried putting the first car on the marker, then putting the engine on the marker, but to no avail.
I complete an operation in a scenario, and it disappears from the F1 task list displayed with the F4 HUD.
However when I display the task list without the F4 HUD (the old-style task list with the green checkmarks and red Xs), it is still marked as incomplete.
What causes the difference?
In this particular case, it is a drop operation in the new "Tucker Industrial" scenario for the Colton Northern route.
The track marker is very short (a few feet long). I tried putting the first car on the marker, then putting the engine on the marker, but to no avail.