Jake makes this plot with output from wcpy gen depo-lines.
It indicates there is probably a bug starting around here:
https://github.com/WireCell/wire-cell-python/blob/master/wirecell/gen/depogen.py#L46
It appears there is some phase space for the wrong bounding box wall to be identified as the one that should terminate the line.
Note, depos outside an WCT AnodePlane active volume are ignored in the simulation so these line extensions are merely cosmetic problems. It would still be nice to fix this someday.