It isn’t affecting us very much right now because it only happen rarely, but it would still be nice if we wouldn’t have wrong steps for the photons.
I was speaking of the other forum post (Error occurs when an optical photon hits the edge of a cubic scintillator - #11 by dsawkey). There you described it with three volumes.
If you have photons hitting an edge, they could get “reflected” into another volume. This could also happen when you have only two volumes (as in the picture: volume A the inside square and volume B the border of the square). Then a photon could be “reflected” into the border volume when it hits an edge.