This is because of the Trim tool within the Matterport Capture app. The trim tool removes 3D data on the "Remove" side of the marker.
In the image below, the trim tool is removing "excess spray" or unwanted 3D data captured from the hallway.
Open the model in Matterport Capture app.
In Mark Features, make sure that the trim marker is just outside the wall. Do not put it directly on top of the wall.
Upload the model again (no additional processing fees). You may have to redo any revisions made in Matterport Workshop.