after restarting the game, two Carved Lumen Quartz lying in the same cell do not combine the brightness in the upper cells.

If two Lumen Quartz crystals are put in one cell, they combine the brightness up to 1500 lux in the upper cells, after restarting game the brightness drops to the correct amount of 1000 lux. And if you move them again and put them in one cell again, the brightness will become higher and further cells again.