Boolean calculation failure due to invalid solid intersections or blocks. Explode blocks; fix coincident faces; eliminate micro-gaps. The selected object is not a valid 3D Solid. Use SOLIDEDIT to check integrity; rebuild from 2D profiles. Error 18026
Regularly check drawing health to fix corruption. autocad error 18003
: If Error 18003 appears across multiple different files, your AutoCAD installation might be damaged. Use the Uninstall/Change option in the Windows Control Panel to Repair or Reinstall the software. fix coincident faces