Peristent Edge Properties
The om file format allows to store meshes together with custom properties. This does not work correctly for edge (and halfedge) properties.
The om file format stores explicitly only vertices and faces (as ordered set of vertices). When reading from a file, edges are created on the fly when they are needed for a face. This means that the edges in the loaded mesh may be in a different order than in the stored mesh.
Edge properties are stored and loaded in the same order. Thus, the loaded edge properties may not correspond to the edge.
I added a unittest which runs into this problem in commit 84eccff6.