Top performer completion percentage changes after victory

If, after any company achieves a victory (beats the objective), any other company after that also achieves a victory, the percentage completion for the top performer goal changes to an incorrect value for all previously victorious companies. The value shouldn't be updated/changed at all once a player is victorious.

This may have to do with how the goal for top performer isn't marked as completed for a company who's achieved victory. Thus, the fix may be as simple as marking all company's objectives complete when they achieve victory.
(screenshot will be added when bug is spotted in-game again)

No files, tests, or entry points are named. Reproduce the issue in OpenTTD with multiple companies achieving victory in sequence, then trace the top performer objective completion state; done means each previously victorious company's completion percentage remains unchanged after later victories.

Written by the indexing model from the issue text.