This is because you have the elements stacked on top of each other, and it's causing problems. Maybe i'll look for a bug, not sure if I can fix anything though
Edit: I do see some odd bugs, if you erase the PHOT first a line horizontally to the right where it's stacked won't be deleted (although really nothing at all should be deleted from the non PHOT stuff). Also deleting the normal elements will delete some photons.