In very rare cases the zone filling algorithm fails in zone calculations. This is due to a non fixed bug in the kbool library (that is a great library do to polygon calculations) used in kicad to handle zones. Currently only one case is known.
A workaround could be to slightly change a zone parameter (like zone clearance) For the known case, a change from 0.381 mm to 0.386 mm solves the problem. -- Jean-Pierre CHARRAS Maître de conférences Directeur d'études 2ieme année. Génie Electrique et Informatique Industrielle 2 Institut Universitaire de Technologie 1 de Grenoble BP 67, 38402 St Martin d'Heres Cedex Recherche : GIPSA-LIS - INPG Rue de la Houille Blanche 38400 Saint Martin d'Heres
