Quick LOD Decimator
The LOD has more triangles than expected
The mesh may contain strongly protected areas, UV borders, sharp edges, or geometry that cannot be simplified safely. Try reducing protection or increasing the Target Ratio.
Shape Keys or Vertex Groups transfer incorrectly
Check the active UV map. A clean, non-overlapping UV layout usually gives the best transfer result.
UV borders lose too much shape
Enable Protect UV Boundary or use a lower UV Boundary Angle. You can also paint extra protection using the Density Group.