Your diagram now gives me more impetus to believe that it is related to the Force-Touch electromagnetic bar which has its contacts grounded to the bottom shell OR the contact between the lower quadrant battery to the ribbon-connector to the other three or four remaining batteries and then into the motherboard. There could be a sort of EMF (electromagnetic force field) interaction in which some sort of safety short trips out and shuts off the force touchpad which then shuts off the screen or vice versa. Most likely vice versa. At this point, this has to be the best explanation and I think it could be a manufacturing flaw because I know mine occurs on the upper quadrant central battery area. So they may have not done a good job of shielding it off since they made all the materials so thin, along with the thin aluminum body or whatever metal it is. For example, many computers and cell phones have thin films in their plastic barrier that does not allow for that to happen. Maybe Apple, in making the design so sleek and thin, betted on leaving it out and it not being a problem, which for now seems to be the case unless you are near a magnet.
Anyhow, see the attached picture and imaging where the keyboard and touchpad are placed on the other side and it makes sense.
