: Sometimes the hardware acceleration is the culprit. You can try setting your AutoCAD executable to "High Performance" or "Power Saving" in your Windows Graphics Settings to see if it stabilizes the engine.
: If the file becomes unusable after the error, locate the .BAK file in your project folder, rename its extension to .DWG , and attempt to reopen it.
: Redundant vertices, micro-gaps between surfaces, or coincident faces (overlapping perfectly).