Periodic conditions fail for curves with the same start/end points.
Periodic conditions fail when surface is composed of two curves with the same start and end points: for example straight line and circle arc. Below is the sample code:
SetFactory("OpenCASCADE");
Box(1) = { 0, 0, 0, 1, 1, 1 };
Cylinder(2) = { 0.58, 0.917, 0.689, -0.004387, 0.006, 0.00668, 0.1, 2*Pi };
Cylinder(3) = { 0.58, -0.083, 0.689, -0.004387, 0.006, 0.00668, 0.1, 2*Pi };
BooleanIntersection{ Volume{ 2:3 }; Delete; } { Volume{ 1 }; }
BooleanDifference{ Volume{ 1 }; Delete; } { Volume{ 2:3 }; }
Periodic Surface{ 17 } = { 15 } Translate{ 0,1,0 };
Mesh 3;
Edited by Christophe Geuzaine