Perfect Scan - But Not Level!

It really depends on the way how the object is captured and how good was GPS signal during capturing (this is changing). There weren’t any changes in the alignment process between the updates.
No other settings to adjust this. You can also use some measured GCPs and let them to georeferenced your model, not the camera priors.

As the scale is important for you I wouldn’t consider the scale from such drones as precise. In this case it is better to have some solid scale placed next to the house during capturing and using that to scale your model.
We can’t do such recommendation.