[Mars409]

I just fixed a problem that showed up with similar error message during decomposePar.

After running 'checkMesh -allTopology -allGeometry', it turns out that I had deleted one patch in constant/polyMesh/boundary that came from the blockMeshDict, as advised in Callum Douglas' Youtube video on snappyHexMesh.

It turns out that the STL geometry has slightly exceeded the blockMeshDict's bounding box, due to editing the geometry in the CAD tool.

All went well after the vertices' coordinates specified in blockMeshDict were amended to fully enclose the STL geometry.

Lesson: if the constant/polyMesh/boundary has a patch that comes from the block mesh, it's likely the bounding box is too small for the STL geometry and needs moving the offending plane outwards in blockMeshDict.