Occasionally, after processing a dataset, when it is viewed through the platform it will present at a different height to the base map, and so will appear either sunken or raised.
This can occur for a couple of reasons. Some drone manufacturers record altitude information, which is often relative to the takeoff height instead of actual GPS altitude information.
The result is that reconstructions of the site may be inaccurate after processing and why they sometimes rendered as "sunken" or "below the ground" is caused by differences between the base maps assumption of a perfect ellipsoidal earth and the actual shape of the planet.
Your data is presented 100% at the correct actual height, it's just that the base map is slightly off. One method of changing the underlying base map so that the height discrepancy is less obvious it to change the base map to Bing Maps Roads from the Map Settings.
How can I fix it?
With some additional manual steps this can be resolved. If you are aware of the existence of any survey marks or known heights this can help, if not we can take rough manual steps to correct this issue for legacy data.