To anyone else following this topic: @pwharton shared an example via PM and it turns out that the issue is the SketchUp 2019 variation of the stray text bug that plagued earlier versions. This bug is triggered when you attach a leader text to an entity (especially a face) and then subsequently edit the model in a way that cause SketchUp to delete that face or merge it with another adjacent face. Before 2019 the text would fly off to an impossible distance, causing severe issues in zoom and orbit. In 2019 it stays near where it should be but can lose its attachment to the original geometry (which was deleted) and come to point at nothing. The fixup evidently detects this situation and deletes the stray text.