This error happens due to a problem when using the scenery with Navigraph. Navigraph places some runways where MSFS has not yet created those runways.
When loading Flight Simulator, it loads in an order where the scenery runway and the Navigraph appear together.
Unfortunately, until January 3rd, there is still no solution for products purchased through the marketplace. We have open support tickets with Navigraph and with Microsoft where one is puts the blame on the other.
If you want to know more details, see this discussion on the Navigraph forum
https://forum.navigraph.com/t/sbjh-duplicated-runway/10671/9
Still want a solution? Please contact us so we can help you in any way.
Didn't buy it on the marketplace? We have a solution for those who bought elsewhere
Edited on January 4th
User Fabio Mac found a solution, tested it and report how to fix it temporarily.
1. Locate the "geardownsimulations-sbjh-airport" folder inside the "Official/OneStore" folder
2. Move the "geardownsimulations-sbjh-airport" folder to the Community folder. Remember to move, not copy so that the folder is not duplicated.
3. Open Flight Simulator, and follow the steps in this tutorial
4. Restart the simulator
Remembering that every time new updates come out, you will need to do these steps again.
This is a temporary solution, to use the scenery until Asobo and Navigraph solve the problem.