strange result with blockMesh and checkMesh
 

Hi all,
I'am a beginner with OF, and try to mesh a square pipe with two inlets and two oulets.
At the junction points I use hex with block with 5 faces like user guide 5.3.3 creating blocks with fewer than 8 vertices.
I test the mesh block by block from inlet to oulet. With 2 inlets, 1 oulet no problem, the junction is correctly meshed with prism and hex.
After I add the second junction with the same technic of meshinig, checkMesh find skewFaces and zeroAreaFaces.
I change unit from m to mm, coordinates to have all positives, look forum but I dont understand why I obtain these bad Faces ?
I add my blockMeshDict file zipped, it contains more vertice than necessary because I keep only the part with problems.
If you have any idea, thank you for helping...