Visualization of tin-created DEMs in QGIS via threejs results in tall 'church-spiral-like' column?

Visualization of tin-created DEMs in QGIS via threejs results in tall 'church-spiral-like' column?

I keep having this problem while doing a simple 3D visualization of my newly created DEM in QGIS via the threejs plugin.

I work in Balkan Zone 7 metric system and, when I try to visualise the DEM ...