Hi,

it seems zero length detection fails on finding very small arcs.
As in previous 3.0.0 release the script ZeroLengthDetection.js was given, I found that the related line is #65 :

      } else if (isArcEntity(entity)) {
          if (entity.getRadius() <= this.distanceTolerance

should be

      } else if (isArcEntity(entity)) {
          if (entity.getLength() <= this.distanceTolerance

because a big radius with a very small angle will yield a very small arc length ...

Since 3.0.0 or so, the ZeroLengthDetection.js script seems to have been binarized in plugins/libqcadproscripts.so, and is not easily correctible any more ...