If you have a custom model and then go to the Model Data to look at the layout and then click Cancel, when you click on the house preview screen, the model will disappear. (clicking OK doesn't cause the bug)
If you need more information or a video, let me know. This is not a problem in 2020.11 but is in 2020.12
After a little more research, hitting cancel changes the scale to 1500 on all axis and x,y,z coordinates to 0 so it is actually so huge that you can't see it
