It is might be a display bug. I updated my bank slot to 120 slots. However sometimes my stuff just vanished from one char. The slot will show for example, 112/120, but I could not fill anything inside, and a message will show ,"your inventory is full". At same time, the char could not use the vanished items. I put my trait researching gears in the bank, and they were not displayed. So then I could not research them because of it until I changed to my alt and took the item out and put them in again. It happened several times to me already. It is not a big issue, however really convenient.