Unwanted linework appears when opening drawings in AutoCAD 2015/2016 Issue
When you open an older drawing file in AutoCAD 2015 or later, the drawing displays unwanted linework that cannot be selected or erased. The linework appears to be randomly displayed.
Causes: The following graphics cards have been reported to encounter this behavior: AMD ATI Radeon HD 3400 series (with 256 MB of RAM) AMD ATI FirePro 2260 AMD ATI FirePro V3700 AMD ATI Radeon HD 4250 The issue is not exclusive to these cards. Solution: To remove the unwanted linework display: Set the LINESMOOTHING system variable to OFF, or Enter 3DCONFIG at the command line and switch Hardware Acceleration OFF. To turn off LINESMOOTHING in AutoCAD 2016: First, set the HQGEOM system variable (High Quality Geometry) to 0. Then set LINESMOOTHING to OFF.