I just downloaded the experimental update on 5/2/2019 today and loading a auto save game of mine. I took out 9 Power Cells from various machines to move to other machines. I had a stack of 9 when I went to a different machine and tried to place a power cell, I double clicked my stack of 9 to do so. (some people drag it, but you can double click it) It placed one in the machine but the rest of the stack vanished permanently. I did this with a couple of other cells in a stack earlier and the same thing happened. Had to reload saved game. I didn't try it a third time.